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<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE rfc [
<!ENTITY RFC1034 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.1034.xml">
<!ENTITY RFC1035 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.1035.xml">
<!ENTITY RFC2119 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml">
<!--<!ENTITY RFC2693 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2693.xml">-->
<!ENTITY RFC2782 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.2782.xml">
<!ENTITY RFC3629 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3629.xml">
<!ENTITY RFC3686 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3686.xml">
<!ENTITY RFC3826 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3826.xml">
<!ENTITY RFC4033 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.4033.xml">
<!ENTITY RFC5237 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5237.xml">
<!--<!ENTITY RFC3912 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.3912.xml">-->
<!ENTITY RFC5869 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5869.xml">
<!ENTITY RFC5890 PUBLIC '' "http://xml.resource.org/public/rfc/bibxml/reference.RFC.5890.xml">
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]>
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<rfc xmlns:xi="http://www.w3.org/2001/XInclude" category="info" docName="draft-schanzen-gns-15" ipr="trust200902" obsoletes="" updates="" submissionType="IETF" xml:lang="en" version="3">
 <!-- xml2rfc v2v3 conversion 2.26.0 -->
 <front>
  <title abbrev="The GNU Name System">
   The GNU Name System
  </title>
  <seriesInfo name="Internet-Draft" value="draft-schanzen-gns-15"/>
  <author fullname="Martin Schanzenbach" initials="M." surname="Schanzenbach">
   <organization>Fraunhofer AISEC</organization>
   <address>
    <postal>
     <street>Lichtenbergstrasse 11</street>
     <city>Garching</city>
     <code>85748</code>
     <country>DE</country>
    </postal>
    <email>martin.schanzenbach@aisec.fraunhofer.de</email>
   </address>
  </author>
  <author fullname="Christian Grothoff" initials="C." surname="Grothoff">
   <organization>Berner Fachhochschule</organization>
   <address>
    <postal>
     <street>Hoeheweg 80</street>
     <city>Biel/Bienne</city>
     <code>2501</code>
     <country>CH</country>
    </postal>
    <email>grothoff@gnunet.org</email>
   </address>
  </author>
  <author fullname="Bernd Fix" initials="B." surname="Fix">
   <organization>GNUnet e.V.</organization>
   <address>
    <postal>
     <street>Boltzmannstrasse 3</street>
     <city>Garching</city>
     <code>85748</code>
     <country>DE</country>
    </postal>
    <email>fix@gnunet.org</email>
   </address>
  </author>

  <!-- Meta-data Declarations -->
  <area>General</area>
  <workgroup>Independent Stream</workgroup>
  <keyword>name systems</keyword>
  <abstract>
    <t>
      This document contains the GNU Name System (GNS) technical
      specification.
      GNS is a decentralized and censorship-resistant name
      system that provides a privacy-enhancing alternative to the Domain
      Name System (DNS).
      <!-- GNS is more. it is also extensible and more flexible -->
    </t>
    <t>
      This document defines the normative wire format of resource records,
      resolution processes, cryptographic routines and security
      considerations for use by implementers.
    </t>
    <t>
      This specification was developed outside the IETF and does not have
      IETF consensus.  It is published here to inform readers about the
      function of GNS, guide future GNS implementations, and ensure
      interoperability among implementations including with the pre-existing
      GNUnet implementation.
    </t>
  </abstract>
 </front>
 <middle>
   <section anchor="introduction" numbered="true" toc="default">
     <name>Introduction</name>
     <t>
       The Domain Name System (DNS) <xref target="RFC1035" /> is a unique
       distributed database and a vital service for most Internet applications.
       While DNS is distributed, in practice it
       relies on centralized, trusted registrars to provide globally unique
       names. As the awareness of the central role DNS plays on the Internet
       rises, various institutions are using their power (including legal means)
       to engage in attacks on the DNS, thus threatening the global availability
       and integrity of information on the Internet.
     </t>
     <t>
       DNS was not designed with security in mind. This makes it very
       vulnerable, especially to attackers that have the technical capabilities
       of an entire nation state at their disposal.
       While a wider discussion of this issue is out of scope for this document,
       analyses and investigations can be found in recent academic research
       works including <xref target="SecureNS"/>.
     </t>
     <t>
       This specification describes a censorship-resistant, privacy-preserving
       and decentralized name system: The GNU Name System (GNS) <xref target="GNS" />.
       It is designed to provide a secure, privacy-enhancing alternative to
       DNS, especially when censorship or manipulation is encountered.
       In particular, it directly addresses concerns in DNS with respect to "Query
       Privacy", the "Single Hierarchy with a Centrally Controlled Root" and
       "Distribution and Management of Root Servers" as raised in
       <xref target="RFC8324"/>.
       GNS can bind names to any kind of
       cryptographically secured token, enabling it to double in some respects as
       an alternative to some of today’s Public Key Infrastructures, in
       particular X.509 for the Web.
     </t>
     <t>
       The design of GNS incorporates the capability to integrate and
       coexist with DNS.
       GNS is based on the principle of a petname system where users can assign
       names to zones.
       It builds on ideas from the Simple Distributed Security
       Infrastructure <xref target="SDSI" />, addressing a central issue with the decentralized
       mapping of secure identifiers to memorable names: namely the impossibility
       of providing a global, secure and memorable mapping without a trusted
       authority. GNS uses the transitivity in the SDSI design to replace the
       trusted root with secure delegation of authority thus making petnames
       useful to other users while operating under a very strong adversary model.
     </t>
     <t>
       This is an important distinguishing factor from the Domain Name System
       where root zone governance is centralized at the Internet Corporation
       for Assigned Names and Numbers (ICANN).
       In DNS terminology, GNS roughly follows the idea of a local
       root zone deployment (see <xref target="RFC8806"/>), with the difference that it is not
       expected that all deployments use the same root zone,
       and that users can easily delegate control of arbitrary domain names to
       arbitrary zones.
     </t>
     <t>
       This document defines the normative wire format of resource records, resolution processes,
       cryptographic routines and security considerations for use by implementers.
     </t>
     <t>
       This specification was developed outside the IETF and does not have
       IETF consensus.  It is published here to guide implementation of GNS
       and to ensure interoperability among implementations.
     </t>
     <section numbered="true" toc="default">
       <name>Requirements Notation</name>
       <t>
         The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
         "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
         "OPTIONAL" in this document are to be interpreted as described in
         BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only
         when, they appear in all capitals, as shown here.
       </t>
     </section>
   </section>
   <section>
     <name>Terminology</name>
     <dl>
       <dt>Apex Label</dt>
       <dd>
         This type of label is used to publish resource
         records in a zone that can be resolved without providing a specific
         label. It is the GNS method to provide what is the "zone apex" in DNS
         <xref target="RFC4033"/>.
         The apex label is represented using the character U+0040 ("@" without
         the quotes).
       </dd>
       <dt>Application</dt>
       <dd>
         A component which uses a GNS implementation
         to resolve names into records and processes its contents.
       </dd>
       <dt>Blinded Zone Key</dt>
       <dd>
         The key derived from a zone key and a label.
         The zone key and the blinded zone key are unlinkable without knowledge of the label.
       </dd>

       <dt>Extension Label</dt>
       <dd>
         The primary use for the extension label is in redirections where the redirection
         target is defined relative to the authoritative zone of the redirection
         record (<xref target="gnsrecords_redirect"/>).
         The extension label is represented using the character U+002B ("+"
         without the quotes).
       </dd>
       <dt>Label Separator</dt>
       <dd>
         Labels in a name are separated using the label separator U+002E
         ("." without the quotes).
         In GNS, with the exceptions of zone Top-Level Domains
         (see below) and boxed records (see <xref target="gnsrecords_box"/>),
         every separator label in a name delegates to another zone.
       </dd>
       <dt>Label</dt>
       <dd>
         A GNS label is a label as defined in <xref target="RFC8499"/>.
         Labels are UTF-8 strings in Unicode
         Normalization Form C (NFC) <xref target="Unicode-UAX15"/>.
         The apex label, label separator and the extension label have
         special purposes in the resolution protocol which are defined
         in the rest of the document.
         Zone administrators <bcp14>MAY</bcp14> disallow certain labels that
         might be easily confused with other labels through registration policies
         (see also <xref target="security_abuse"/>).
       </dd>

       <dt>Name</dt>
       <dd>
         A name in GNS is a domain name as defined in  <xref target="RFC8499"/>
         as an ordered list of labels.
         Names are UTF-8 <xref target="RFC3629" /> strings consisting of the
         list of labels concatenated with a label separator.
         Names are resolved starting from the rightmost label.
         GNS does not impose length restrictions on names or labels.
         However, applications <bcp14>MAY</bcp14> ensure that name and label lengths are
         compatible with DNS and in particular IDNA <xref target="RFC5890"/>.
         In the spirit of <xref target="RFC5895"/>, applications <bcp14>MAY</bcp14> preprocess
         names and labels to ensure compatibility with DNS or support
         specific user expectations, for example according to
         <xref target="Unicode-UTS46"/>.
         A GNS name may be indistinguishable from a DNS name and care must
         be taken by applications and implementors when handling GNS names
         (see <xref target="namespace_ambiguity"/>).
       </dd>
       <dt>Resolver</dt>
       <dd>
         The component of a GNS implementation which provides
         the recursive name resolution logic defined in
         <xref target="resolution"/>.
       </dd>
       <dt>Resource Record</dt>
       <dd>
         A GNS resource record is the information associated with a label in a
         GNS zone.
         A GNS resource record contains information as defined by its
         resource record type.
       </dd>
       <dt>Start Zone</dt>
       <dd>
         In order to resolve any given GNS name an initial start zone must be
         determined for this name.
         The start zone can be explicitly defined through a zTLD.
         Otherwise, it is determined through a local suffix-to-zone mapping
         (see <xref target="governance"/>).
       </dd>

       <dt>Top-Level Domain</dt>
       <dd>
	       The rightmost part of a GNS name is a GNS Top-Level Domain (TLD).
         A GNS TLD can consist of one or more labels.
	 Unlike DNS Top-Level Domains (defined in <xref target="RFC8499"/>),
	 GNS does not expect all users to use the same global root zone. Instead,
         with the exception of Zone Top-Level Domains (see below),
         GNS TLDs are typically part of the configuration of the local resolver
         (see <xref target="governance"/>), and might thus not be globally unique.
       </dd>
       <dt>Zone</dt>
       <dd>
         A GNS zone contains authoritative information (resource records).
         A zone is uniquely identified by its zone key.  Unlike DNS zones,
         a GNS zone does not need to have a SOA record under the apex label.
       </dd>
       <dt>Zone Key</dt>
       <dd>
         A key which uniquely identifies a zone.
         It is usually a public key of an asymmetric key pair.
       </dd>
       <dt>Zone Key Derivation Function</dt>
       <dd>
         The zone key derivation function (ZKDF) blinds a zone key using a label.
       </dd>

       <dt>Zone Master</dt>
       <dd>
         The component of a GNS implementation which provides
         local zone management and publication as defined in
         <xref target="publish"/>.
       </dd>
       <dt>Zone Owner</dt>
       <dd>
         The holder of the secret (typically a private key)
	 that (together with a label and a value to sign) allows the creation of zone
	 signatures that can be validated against the respective blinded zone key.
       </dd>
       <dt>Zone Top-Level Domain</dt>
       <dd>
         A GNS Zone Top-Level Domain (zTLD) is a sequence of GNS labels at
         the end of a GNS name which encodes a zone type and
         zone key of a zone.
         Due to the statistical uniqueness of zone keys, zTLDs are also globally unique.
	 A zTLD label sequence can only be distinguished from ordinary TLD label sequences
         by attempting to decode the labels into a zone type and zone key.
       </dd>

       <dt>Zone Type</dt>
       <dd>
         The type of a GNS zone determines the cipher system and binary encoding
	 format of the zone key, blinded zone keys, and signatures.
       </dd>
     </dl>
   </section>
   <section anchor="overview" numbered="true" toc="default">
     <name>Overview</name>
     <t>
       In GNS, any user can create and manage one or more zones
       (<xref target="zones"/>) as part of a zone master implementation.
       Zones are uniquely identified by a zone key.
       Zone contents are signed using blinded private keys and
       encrypted using derived secret keys.
       The zone type determines the respective set of cryptographic operations
       and the wire formats for encrypted data, public keys and signatures.
     </t>
     <t>
       A zone can be populated with mappings from labels to resource records by
       its owner (<xref target="rrecords"/>).
       A label can be mapped to a delegation record which results in the
       corresponding subdomain being delegated to another zone. Circular
       delegations are explicitly allowed, including delegating a subdomain
       to its immediate parent zone.  In
       order to support (legacy) applications as well as to facilitate the use
       of petnames, GNS defines auxiliary record types in addition to
       supporting existing DNS records.
     </t>
     <t>
       Zone contents are encrypted and signed
       before being published in a key-value storage (<xref target="publish"/>)
       as illustrated in <xref target="figure_arch_publish"/>.
       In this process, unique zone identification is hidden from the network
       through the use of key blinding.
       Key blinding allows the creation of signatures for zone contents
       using a blinded public/private key pair.
       This blinding is realized using a deterministic key
       derivation from
       the original zone key and corresponding private key using record label values
       as blinding factors.
       Specifically, the zone owner can derive blinded private keys for each record
       set published under a label, and a
       resolver can derive the corresponding blinded public keys.
       It is expected that GNS implementations use distributed or decentralized
       storages such as distributed hash tables (DHT) in order to facilitate
       availability within a network without the need for dedicated infrastructure.
       Specification of such a distributed or decentralized storage is out of
       scope of this document, but possible existing implementations include those
       based on <xref target="RFC7363" />, <xref target="Kademlia" /> or
       <xref target="R5N" />.
     </t>
     <figure anchor="figure_arch_publish" title="An example diagram of two hosts publishing GNS zones.">
       <artwork name="" type="" align="left" alt=""><![CDATA[
        Local Host     |   Remote        |    Remote Host
                       |   Storage       |
                       |                 |
                       |    +---------+  |
                       |   /         /|  |
              Publish  |  +---------+ |  |  Publish
  +---------+ Records  |  |         | |  |  Records +---------+
  |  Zone   |----------|->| Record  | |<-|----------|  Zone   |
  | Master  |          |  | Storage | |  |          | Master  |
  +---------+          |  |         |/   |          +---------+
       A               |  +---------+    |               A
       |               |                 |               |
    +---------+        |                 |           +---------+
   /   |     /|        |                 |          /    |    /|
  +---------+ |        |                 |         +---------+ |
  |         | |        |                 |         |         | |
  |  Local  | |        |                 |         |  Local  | |
  |  Zones  | |        |                 |         |  Zones  | |
  |         |/         |                 |         |         |/
  +---------+          |                 |         +---------+
         ]]></artwork>
     </figure>
     <t>
       Applications use the resolver to lookup GNS names.
       Starting from a configurable start zone, names are resolved by following zone
       delegations recursively as illustrated in <xref target="figure_arch_resolv"/>.
       For each label in a name, the recursive GNS resolver
       fetches the respective record from the storage layer (<xref target="resolution"/>).
       Without knowledge of the label values and the zone keys, the
       different derived keys are unlinkable both to the original zone key and to each
       other.
       This prevents zone enumeration (except via impractical online brute
       force attacks) and requires knowledge
       of both the zone key and the label to confirm affiliation of a
       query or the corresponding encrypted record set with a
       specific zone. At the same time, the blinded zone key provides
       resolvers
       with the ability to verify the integrity of the published information
       without disclosing the originating zone.
     </t>
     <figure anchor="figure_arch_resolv" title="High-level view of the GNS resolution process.">
       <artwork name="" type="" align="left" alt=""><![CDATA[
                           Local Host           |   Remote
                                                |   Storage
                                                |
                                                |    +---------+
                                                |   /         /|
                                                |  +---------+ |
+-----------+ Name     +----------+ Recursive   |  |         | |
|           | Lookup   |          | Resolution  |  | Record  | |
|Application|----------| Resolver |-------------|->| Storage | |
|           |<---------|          |<------------|--|         |/
+-----------+ Results  +----------+ Intermediate|  +---------+
                          A         Results     |
                          |                     |
                       +---------+              |
                      /   |     /|              |
                     +---------+ |              |
                     |         | |              |
                     |  Start  | |              |
                     |  Zones  | |              |
                     |         |/               |
                     +---------+                |
         ]]></artwork>
     </figure>

     <t>
       In the remainder of this document, the "implementer" refers to the developer building
       a GNS implementation including the resolver, zone master, and
       supporting configuration such as start zones (<xref target="governance"/>).
     </t>
   </section>
   <section anchor="zones" numbered="true" toc="default">
     <name>Zones</name>
     <t>
       A zone master implementation <bcp14>SHOULD</bcp14> enable the zone
       owners to create and manage zones.
       If this functionality is not implemented, names can still be resolved
       if zone keys for the initial step in the name resolution are available
       (see <xref target="resolution"/>).
     </t>
     <t>
       A zone in GNS is uniquely identified by its zone type and zone key.
       Each zone can be represented by a Zone Top-Level Domain (zTLD) string.
       A zone type (ztype) is a unique 32-bit number.
       This number corresponds to a resource record type number
       identifying a delegation record type
       in the GNUnet Assigned Numbers Authority <xref target="GANA" />.
       The ztype is a unique identifier for the set cryptographic functions
       of the zone and the format of the delegation record type.
       Any ztype <bcp14>MUST</bcp14> define the following set of cryptographic functions:
     </t>
     <dl>
       <dt>KeyGen() -> d, zk</dt>
       <dd>
         is a function to generate a new private key d and
	 the corresponding public zone key zk.
       </dd>
       <dt>ZKDF(zk,label) -> zk'</dt>
       <dd>
         is a zone key derivation function which blinds a zone key zk
         using a label. zk and zk' must be unlinkable. Furthermore,
         blinding zk with different values for the label must result
         in different, unlinkable zk' values.
       </dd>
       <dt>S-Encrypt(zk,label,expiration,message) -> ciphertext</dt>
       <dd>
         is a symmetric encryption function which encrypts the record
         data based on key material derived from the zone key,
         a label, and an expiration timestamp.
         In order to leverage performance-enhancing caching features of certain
         underlying storages, in particular DHTs, a deterministic encryption
         scheme is recommended.
       </dd>
       <dt>S-Decrypt(zk,label,expiration,ciphertext) -> message</dt>
       <dd>
         is a symmetric decryption function which decrypts the encrypted record
         data based on key material derived from the zone key,
         a label, and an expiration timestamp.
       </dd>
       <dt>Sign(d,message) -> signature</dt>
       <dd>
         is a function to sign a message using the private
         key d, yielding an unforgeable cryptographic signature.
         In order to leverage performance-enhancing caching features of certain
         underlying storages, in particular DHTs, a deterministic signature
         scheme is recommended.
       </dd>
       <dt>Verify(zk,message,signature) -> boolean</dt>
       <dd>
         is a function to verify the signature was created using
         the private key d corresponding to the zone key zk
         where d,zk := Keygen().
         The function returns a boolean value of "TRUE" if the signature is valid,
         and otherwise "FALSE".
       </dd>
       <dt>SignDerived(d,label,message) -> signature</dt>
       <dd>
         is a function to sign a message (typically encrypted record data) that
         can be verified using the derived zone key zk' := ZKDF(zk,label).
         In order to leverage performance-enhancing caching features of certain
         underlying storages, in particular DHTs, a deterministic signature
         scheme is recommended.
       </dd>
       <dt>VerifyDerived(zk,label,message,signature) -> boolean</dt>
       <dd>
         is function to verify the signature using the derived zone key
         zk' := ZKDF(zk,label).
         The function returns a boolean value of "TRUE" if the signature is valid,
         and otherwise "FALSE".
       </dd>
     </dl>
     <t>
       The cryptographic functions of the default ztypes are specified with
       their corresponding delegation records in <xref target="gnsrecords_delegation"/>.
       In order to support cryptographic agility, additional ztypes <bcp14>MAY</bcp14>
       be defined in the future which replace or update the default ztypes defined in this
       document.
       All ztypes <bcp14>MUST</bcp14> be registered as dedicated zone delegation
       record types in the GNU Name System Record Types registry (see <xref target="gana"/>).
       When defining new record types the cryptographic security considerations
       of this document apply, in particular <xref target="security_cryptography"/>.
     </t>
     <section anchor="zTLD" numbered="true" toc="default">
       <name>Zone Top-Level Domain</name>
       <t>
         The zTLD is the Zone Top-Level Domain.
         It is a string which encodes the zone type and zone key into a domain name.
         The zTLD is used as a globally unique reference to a specific
         zone in the process of name resolution.
         It is created by encoding a binary concatenation of the zone type and
         zone key (see <xref target="figure_zid"/>).
         The used encoding is a variation of the Crockford Base32 encoding
         <xref target="CrockfordB32"/> called Base32GNS.
         The encoding and decoding symbols for Base32GNS including this
         modification are defined in the table found in <xref target="CrockfordB32Encode"/>.
         The functions for encoding and decoding based on this table are called
         Base32GNS-Encode and Base32GNS-Decode, respectively.
       </t>
<figure anchor="figure_zid" title="The decoded binary representation of the zTLD">
       <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|       ZONE TYPE       |      ZONE KEY         /
+-----+-----+-----+-----+                       /
/                                               /
/                                               /
         ]]></artwork>
     </figure>
       <t>
         Consequently, a zTLD is encoded and decoded as follows:
       </t>
       <artwork name="" type="" align="left" alt=""><![CDATA[
zTLD := Base32GNS-Encode(ztype||zkey)
ztype||zkey := Base32GNS-Decode(zTLD)
         ]]></artwork>
       <t>
         where "||" is the concatenation operator.
       </t>
       <t>
         The zTLD can be used as-is as a rightmost label in a GNS name.
         If an application wants to ensure DNS compatibility of the name,
         it <bcp14>MAY</bcp14> also represent the zTLD as follows:
         If the zTLD is less than or equal to 63 characters, it can
         be used as a zTLD as-is.
         If the zTLD is longer than 63 characters, the
         zTLD is divided into smaller labels separated by the label separator.
         Here, the most significant bytes of the "ztype||zkey" concatenation
         must be contained in the rightmost label of the resulting string and
         the least significant bytes in the leftmost label of the resulting string. This allows the
         resolver to determine the ztype and zTLD length from the rightmost
         label and to subsequently determine how many labels the zTLD should span.
         A GNS implementation <bcp14>MUST</bcp14> support the division of zTLDs
         in DNS compatible label lengths.
         For example, assuming a zTLD of 130 characters, the division is:
       </t>
       <!-- FIXME: Is this really really necessary? Really? -->
       <artwork name="" type="" align="left" alt=""><![CDATA[
zTLD[126..129].zTLD[63..125].zTLD[0..62]
         ]]></artwork>
   </section>
    <section anchor="revocation" numbered="true" toc="default">
       <name>Zone Revocation</name>
       <t>
         In order to revoke a zone key, a signed revocation message <bcp14>MUST</bcp14> be
         published.
         This message <bcp14>MUST</bcp14> be signed using the private key.
         The revocation message is broadcast to the network.
         The specification of the broadcast mechanism is out of scope for this
         document.
         A possible broadcast mechanism for efficient flooding in a distributed
         network is implemented in <xref target="GNUnet"/>.
         Alternatively, revocation messages could also be distributed via a
         distributed ledger or a trusted central server.
         To prevent
         flooding attacks, the revocation message <bcp14>MUST</bcp14> contain a proof of work
         (PoW).
         The revocation message including the PoW <bcp14>MAY</bcp14> be calculated
         ahead of time to support timely revocation.
       </t>
       <t>
         For all occurrences below, "Argon2id" is the Password-based Key
         Derivation Function as defined in <xref target="RFC9106" />. For the
         PoW calculations the algorithm is instantiated with the
         following parameters:
       </t>
       <dl>
         <dt>S</dt>
         <dd>The salt. Fixed 16-byte string: "GnsRevocationPow".</dd>
         <dt>t</dt>
         <dd>Number of iterations: 3</dd>
         <dt>m</dt>
         <dd>Memory size in KiB: 1024</dd>
         <dt>T</dt>
         <dd>Output length of hash in bytes: 64</dd>
         <dt>p</dt>
         <dd>Parallelization parameter: 1</dd>
         <dt>v</dt>
         <dd>Algorithm version: 0x13</dd>
         <dt>y</dt>
         <dd>Algorithm type (Argon2id): 2</dd>
         <dt>X</dt><dd>Unused</dd>
         <dt>K</dt><dd>Unused</dd>
       </dl>
       <t>
         <xref target="figure_revocation"/> illustrates the format
         of the data "P" on which the PoW is calculated.
       </t>
       <figure anchor="figure_revocation" title="The Format of the PoW Data.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      POW                      |
+-----------------------------------------------+
|                   TIMESTAMP                   |
+-----------------------------------------------+
|       ZONE TYPE       |    ZONE KEY           |
+-----+-----+-----+-----+                       |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>POW</dt>
         <dd>
           A 64-bit value that is a solution to the PoW. In network byte order.
         </dd>
         <dt>TIMESTAMP</dt>
         <dd>
           denotes the absolute 64-bit date when the revocation was computed.
           In microseconds since midnight (0 hour), January 1, 1970 UTC in network
           byte order.
         </dd>
         <dt>ZONE TYPE</dt>
         <dd>
           is the 32-bit zone type.
         </dd>
         <dt>ZONE KEY</dt>
         <dd>
           is the 256-bit public key zk of the zone which is being revoked.
           The wire format of this value is defined by the ZONE TYPE.
         </dd>
       </dl>
       <t>
         Usually, PoW schemes require to find one POW value such that
         at least D leading zeroes are found in the hash result.
         D is then referred to as the difficulty of the PoW.
         In order to reduce the variance in time it takes to calculate the
         PoW, a valid GNS revocation requires that a number Z different PoWs
         must be found that on average have D leading zeroes.
       </t>
       <t>
         The resulting proofs are ready for dissemination.
         The concrete
         dissemination and publication methods are out of scope of this
         document. Given an average difficulty of D, the proofs have an
         expiration time of EPOCH. With each additional bit difficulty, the
         lifetime of the proof is prolonged for another EPOCH.
         Consequently, by calculating a more difficult PoW, the lifetime of the
         proof can be increased on demand by the zone owner.
       </t>
       <t>
         The parameters are defined as follows:
       </t>
       <dl>
         <dt>Z</dt>
         <dd>The number of PoWs that are required. Its value is fixed at 32.</dd>
         <dt>D</dt>
         <dd>The minimum average difficulty. Its value is fixed at 22.</dd>
         <dt>EPOCH</dt>
         <dd>A single epoch. Its value is fixed at 365 days in microseconds.</dd>
       </dl>
       <t>
         The revocation message wire format is illustrated in
         <xref target="figure_revocationdata"/>.
       </t>
       <figure anchor="figure_revocationdata" title="The Revocation Message Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   TIMESTAMP                   |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      TTL                      |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                     POW_0                     |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                       ...                     |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                     POW_Z-1                   |
+-----------------------------------------------+
|       ZONE TYPE       |    ZONE KEY           |
+-----+-----+-----+-----+                       |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   SIGNATURE                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>TIMESTAMP</dt>
         <dd>
           denotes the absolute 64-bit date when the revocation was computed.
           In microseconds since midnight (0 hour), January 1, 1970 UTC in network
           byte order. This is the same value as the time stamp used in the
           individual PoW calculations.
         </dd>
         <dt>TTL</dt>
         <dd>
           denotes the relative 64-bit time to live of the record in
           microseconds in network byte order.
           The field <bcp14>SHOULD</bcp14> be set to EPOCH * 1.1.
           Given an average number of leading zeros D', then the field value
           <bcp14>MAY</bcp14> be increased up to (D'-D) * EPOCH * 1.1.
           Validators <bcp14>MAY</bcp14> reject messages with lower or higher
           values when received.
           The EPOCH is extended by
           10% in order to deal with unsynchronized clocks.
         </dd>
         <dt>POW_i</dt>
         <dd>
           The values calculated as part of the PoW, in network byte order.
           Each POW_i <bcp14>MUST</bcp14> be unique in the set of POW values.
           To facilitate fast verification
           of uniqueness, the POW values must be given in strictly
           monotonically increasing order in the message.
         </dd>
         <dt>ZONE TYPE</dt>
         <dd>
           The 32-bit zone type corresponding to the zone key.
         </dd>
         <dt>ZONE KEY</dt>
         <dd>
           is the public key zk of the zone which is being revoked and
           the key to be used to verify SIGNATURE.
         </dd>
         <dt>SIGNATURE</dt>
         <dd>
           A signature over a time stamp and the zone zk of the zone
           which is revoked and corresponds to the key used in the PoW.
           The signature is created using the Sign() function of
           the cryptosystem of the zone and the private key
           (see <xref target="zones" />).
         </dd>
       </dl>
       <!-- FIXME Do we really need a purpose? -->
      <t>
        The signature over the public key covers a 32-bit header
        prefixed to the time stamp and public key fields.
        The header includes the key length and signature purpose.
        The wire format is illustrated
        in <xref target="figure_revsigwithpseudo"/>.
       </t>
       <figure anchor="figure_revsigwithpseudo" title="The Wire Format of the Revocation Data for Signing.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|         SIZE          |       PURPOSE (0x03)  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   TIMESTAMP                   |
+-----+-----+-----+-----+-----+-----+-----+-----+
|       ZONE TYPE       |     ZONE KEY          |
+-----+-----+-----+-----+                       |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>SIZE</dt>
         <dd>
           A 32-bit value containing the length of the signed data in bytes
           in network byte order.
         </dd>
         <dt>PURPOSE</dt>
         <dd>
           A 32-bit signature purpose flag.
           The value of this field <bcp14>MUST</bcp14> be 3.
           The value is encoded in network byte order.
           It defines the context in which
           the signature is created so that it cannot be reused in other parts
           of the protocol including possible future extensions.
           The value of this field corresponds to an entry in the
           GANA "GNUnet Signature Purpose" registry <xref target="gana"/>.
         </dd>
         <dt>TIMESTAMP</dt>
         <dd>
           Field as defined in the revocation message above.
         </dd>
         <dt>ZONE TYPE</dt>
         <dd>
           Field as defined in the revocation message above.
         </dd>
         <dt>ZONE KEY</dt>
         <dd>Field as defined in the revocation message above.</dd>
       </dl>
       <t>
         In order to validate a revocation the following steps <bcp14>MUST</bcp14> be taken:
       </t>
       <ol>
         <li>The signature <bcp14>MUST</bcp14> be verified against the zone key.</li>
         <li>The set of POW values <bcp14>MUST</bcp14> NOT contain duplicates which <bcp14>MUST</bcp14> be checked by verifying that the values are strictly monotonically increasing.</li>
         <li>The average number of leading zeroes D' resulting from the provided
         POW values <bcp14>MUST</bcp14> be greater than and not equal to D.  Implementers
         <bcp14>MUST NOT</bcp14> use an integer data type to calculate or represent D'.</li>
       </ol>
       <t>
         The TTL field in the revocation message is informational.
         A revocation <bcp14>MAY</bcp14> be discarded without checking the POW
         values or the signature if the TTL (in combination with TIMESTAMP)
         indicates that the revocation has already expired.
         The actual validity period of the
         revocation <bcp14>MUST</bcp14> be determined by examining the leading
         zeroes in the POW values.
       </t>
       <t>
         The validity period of the revocation is calculated as
         (D'-D) * EPOCH * 1.1. The EPOCH is extended by
         10% in order to deal with unsynchronized clocks.
         The validity period added on top of the TIMESTAMP yields the
         expiration date.
         If the current time is after the expiration date, the
         revocation is considered stale.
       </t>
       <t>
         Verified revocations <bcp14>MUST</bcp14> be stored locally.
         The implementation <bcp14>MAY</bcp14> discard stale revocations and
         evict then from the local store at any time.
       </t>
       <t>
         Implementations <bcp14>MUST</bcp14> broadcast received revocations
         if they are valid and not stale.
         Should the calculated validity period differ from the TTL field value,
         the calculated value <bcp14>MUST</bcp14> be used as TTL field value
         when forwarding the revocation message.
         Systems might disagree on the current time, so implementations
         <bcp14>MAY</bcp14> use stale but otherwise valid
         revocations but <bcp14>SHOULD NOT</bcp14> broadcast them.
         Forwarded stale revocations <bcp14>MAY</bcp14> be discarded.
       </t>
       <t>
         Any locally stored revocation <bcp14>MUST</bcp14> be considered during
         delegation record processing (<xref target="delegation_processing"/>).
       </t>
     </section>


   </section>
   <section anchor="rrecords" numbered="true" toc="default">
     <name>Resource Records</name>
     <t>
       A GNS implementation <bcp14>SHOULD</bcp14> provide a mechanism to create and manage local
       zones as well as a persistence mechanism such as a database for resource
       records.
       A new local zone is established by selecting a zone type and creating a
       zone key pair.
       If this mechanism is not implemented,
       no zones can be published in the storage (<xref target="publish"/>)
       and name resolution is limited to non-local start zones
       (<xref target="governance"/>).
     </t>
     <t>
       A GNS resource record holds the data of a specific record in a zone.
       The resource record format is defined in
       <xref target="figure_gnsrecord"/>.
     </t>
     <figure anchor="figure_gnsrecord" title="The Resource Record Wire Format.">
       <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|    SIZE   |   FLAGS   |          TYPE         |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      DATA                     /
/                                               /
/                                               /
         ]]></artwork>
     </figure>
     <dl>
       <dt>EXPIRATION</dt>
       <dd>
         denotes the absolute 64-bit expiration date of the record.
         In microseconds since midnight (0 hour), January 1, 1970 UTC in network
         byte order.
       </dd>
       <dt>SIZE</dt>
       <dd>
         denotes the 16-bit size of the DATA field in bytes and in network byte
         order.
       </dd>
       <dt>FLAGS</dt>
       <dd>
         is a 16-bit resource record flags field (see below).
       </dd>
       <dt>TYPE</dt>
       <dd>
         is the 32-bit resource record type. This type can be one of the GNS resource
         records as defined in <xref target="rrecords" /> or a DNS record
         type as defined in <xref target="RFC1035" /> or any of the
         complementary standardized DNS resource record types. This value must be
         stored in network byte order. Note that values
         below 2^16 are reserved for 16-bit DNS Resorce Record types allocated by IANA <xref target="RFC6895" />.
         Values above 2^16 are allocated by the
         GNUnet Assigned Numbers Authority <xref target="GANA" />.
       </dd>
       <dt>DATA</dt>
       <dd>
         the variable-length resource record data payload. The content is defined
         by the
         respective type of the resource record.
       </dd>
     </dl>
     <t>
       Flags indicate metadata surrounding the resource record.
       An application creating resource records <bcp14>MUST</bcp14> set all bits
       to 0 unless it wants to set the respective flag.
       As additional flags can be defined in future protocol versions,
       if an application or implementation encounters a flag which it does not
       recognize, it <bcp14>MUST</bcp14> be ignored.
       Any combination of the flags specified below are valid.
       <xref target="figure_flag"/>
       illustrates the flag distribution in the 16-bit flag field of a
       resource record:
     </t>
     <figure anchor="figure_flag" title="The Resource Record Flag Wire Format.">
       <artwork name="" type="" align="left" alt=""><![CDATA[
0           13            14      15
+--------...+-------------+-------+---------+
| Reserved  |SUPPLEMENTAL |SHADOW |CRITICAL |
+--------...+-------------+-------+---------+
         ]]></artwork>
     </figure>
     <dl>
       <dt>CRITICAL</dt>
       <dd>
         If this flag is set, it indicates that processing is critical.
         Implementations that do not support the record type or are otherwise
         unable to process the record <bcp14>MUST</bcp14> abort resolution upon encountering
         the record in the resolution process.
       </dd>
       <dt>SHADOW</dt>
       <dd>
         If this flag is set, this record <bcp14>MUST</bcp14> be ignored by resolvers unless all (other)
         records of the same record type have expired.  Used to allow zone publishers to
         facilitate good performance when records change by allowing them to put future
         values of records into the storage.
         This way, future values can propagate and can be
         cached before the transition becomes active.
       </dd>
       <dt>SUPPLEMENTAL</dt>
       <dd>
         This is a supplemental record. It is provided in addition to the
         other records. This flag indicates that this record is not explicitly
         managed alongside the other records under the respective name but
         might be useful for the application.
       </dd>
     </dl>
   <section anchor="gnsrecords_delegation" numbered="true" toc="default">
     <name>Zone Delegation Records</name>
     <t>
       This section defines the initial set of zone delegation record types.
       Any implementation <bcp14>SHOULD</bcp14> support all zone types defined here and
       <bcp14>MAY</bcp14> support any number of additional delegation records defined in
       the GNU Name System Record Types registry (see <xref target="gana"/>).
       Not supporting some zone types will result in resolution failures in case
       the respective zone type is encountered.
       This is be a valid choice if some zone delegation record types have been
       determined to be cryptographically insecure.
       Zone delegation records <bcp14>MUST NOT</bcp14> be stored and published
       under the apex label.
       A zone delegation record type value is the same as the respective ztype
       value.
       The ztype defines the cryptographic primitives for the zone that is
       being delegated to.
       A zone delegation record payload contains the public key of
       the zone to delegate to.
       A zone delegation record <bcp14>MUST</bcp14> have the CRITICAL flag set
       and <bcp14>MUST</bcp14> be the only non-supplemental record under a label.
       There <bcp14>MAY</bcp14> be inactive records of the same type which have
       the SHADOW flag set in order to facilitate smooth key rollovers.
     </t>
     <t>
       In the following, "||" is the concatenation operator of two byte strings.
       The algorithm specification uses character strings such as GNS labels or
       constant values.
       When used in concatenations or as input to functions the
       null-terminator of the character strings <bcp14>MUST NOT</bcp14> be
       included.
     </t>
     <section anchor="gnsrecords_pkey" numbered="true" toc="default">
       <name>PKEY</name>
       <t>
         In GNS, a delegation of a label to a zone of type "PKEY" is
         represented through a PKEY record.  The PKEY DATA entry wire format can be found in <xref target="figure_pkeyrecord"/>.
       </t>
       <figure anchor="figure_pkeyrecord" title="The PKEY Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   PUBLIC KEY                  |
|                                               |
|                                               |
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>PUBLIC KEY</dt>
         <dd>
           A 256-bit Ed25519 public key.
         </dd>
       </dl>

       <t>
         For PKEY zones the zone key material is derived using the
         curve parameters of the twisted Edwards representation
         of Curve25519 <xref target="RFC7748" /> (a.k.a. Ed25519)
         with the ECDSA scheme <xref target="RFC6979" />.
         The following naming convention is used for the cryptographic primitives of PKEY zones:
       </t>
       <dl>
         <dt>d</dt>
         <dd>
           is a 256-bit Ed25519 private key (private scalar).
         </dd>
         <dt>zk</dt>
         <dd>
           is the Ed25519 public zone key corresponding to d.
         </dd>
         <dt>p</dt>
         <dd>
           is the prime of edwards25519 as defined in <xref target="RFC7748" />, i.e.
           2^255 - 19.
         </dd>
         <dt>G</dt>
         <dd>
           is the group generator (X(P),Y(P)) of edwards25519 as defined in
           <xref target="RFC7748" />.
         </dd>
         <dt>L</dt>
         <dd>
           is the order of the prime-order subgroup of edwards25519 in <xref target="RFC7748" />.
         </dd>
         <dt>KeyGen()</dt>
         <dd>The generation of the private
           scalar d and the curve point zk := d*G (where G is the group generator
           of the elliptic curve) as defined in Section 2.2. of
           <xref target="RFC6979" /> represents the KeyGen() function.
         </dd>
       </dl>
       <t>
         The zone type and zone key of a PKEY are 4 + 32 bytes in length. This means that
         a zTLD will always fit into a single label and does
         not need any further conversion.
         Given a label, the output zk' of the ZKDF(zk,label) function is
         calculated as follows for PKEY zones:
       </t>
       <artwork name="" type="" align="left" alt=""><![CDATA[
ZKDF(zk,label):
  PRK_h := HKDF-Extract ("key-derivation", zk)
  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
  zk' := (h mod L) * zk
  return zk'
        ]]></artwork>
       <t>
         The PKEY cryptosystem uses a hash-based key derivation function (HKDF) as defined in
         <xref target="RFC5869" />, using SHA-512 <xref target="RFC6234"/> for the extraction
         phase and SHA-256 <xref target="RFC6234"/> for the expansion phase.
         PRK_h is key material retrieved using an HKDF using the string
         "key-derivation" as salt and the zone key as initial
         keying material.
         h is the 512-bit HKDF expansion result and must be interpreted in
         network byte order. The expansion information input is
         a concatenation of the label and the string "gns".
         The multiplication of zk with h is a point multiplication,
         while the multiplication of d with h is a scalar multiplication.
       </t>
       <t>
         The Sign() and Verify() functions
         for PKEY zones are implemented using 512-bit ECDSA deterministic
         signatures as specified in <xref target="RFC6979" />.
         The same functions can be used for derived keys:
       </t>
         <artwork name="" type="" align="left" alt=""><![CDATA[
SignDerived(d,label,message):
  zk := d * G
  PRK_h := HKDF-Extract ("key-derivation", zk)
  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
  d' := (h * d) mod L
  return Sign(d',message)
           ]]></artwork>
         <t>
           A signature (R,S) is valid if the following holds:
         </t>
         <artwork name="" type="" align="left" alt=""><![CDATA[
VerifyDerived(zk,label,message,signature):
  zk' := ZKDF(zk,label)
  return Verify(zk',message,signature)
           ]]></artwork>
       <t>
         The S-Encrypt() and S-Decrypt() functions use AES in counter mode
         as defined in <xref target="MODES" /> (CTR-AES-256):
       </t>
         <artwork name="" type="" align="left" alt=""><![CDATA[
S-Encrypt(zk,label,expiration,plaintext):
  PRK_k := HKDF-Extract ("gns-aes-ctx-key", zk)
  PRK_n := HKDF-Extract ("gns-aes-ctx-iv", zk)
  K := HKDF-Expand (PRK_k, label, 256 / 8)
  NONCE := HKDF-Expand (PRK_n, label, 32 / 8)
  IV := NONCE || expiration || 0x0000000000000001
  return CTR-AES256(K, IV, plaintext)

S-Decrypt(zk,label,expiration,ciphertext):
  PRK_k := HKDF-Extract ("gns-aes-ctx-key", zk)
  PRK_n := HKDF-Extract ("gns-aes-ctx-iv", zk)
  K := HKDF-Expand (PRK_k, label, 256 / 8)
  NONCE := HKDF-Expand (PRK_n, label, 32 / 8)
  IV := NONCE || expiration || 0x0000000000000001
  return CTR-AES256(K, IV, ciphertext)
           ]]></artwork>
       <t>
         The key K and counter IV are derived from
         the record label and the zone key zk using a hash-based key
         derivation function (HKDF) as defined in <xref target="RFC5869" />.
         SHA-512 <xref target="RFC6234"/> is used for the
         extraction phase and SHA-256 <xref target="RFC6234"/> for the expansion phase.
         The output keying material is 32 bytes (256 bits) for the symmetric
         key and 4 bytes (32 bits) for the nonce.
         The symmetric key K is a 256-bit AES <xref target="RFC3826" /> key.
       </t>
       <t>
         The nonce is combined with a 64-bit initialization vector and a
         32-bit block counter as defined in <xref target="RFC3686" />.
         The block counter begins with the value of 1, and it is incremented
         to generate subsequent portions of the key stream.
         The block counter is a 32-bit integer value in network byte order.
         The initialization vector is the expiration time of the
         resource record block in network byte order.
         The resulting counter (IV) wire format can be found in
         <xref target="figure_hkdf_ivs_pkey"/>.
       </t>
       <figure anchor="figure_hkdf_ivs_pkey" title="The Block Counter Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32
+-----+-----+-----+-----+
|         NONCE         |
+-----+-----+-----+-----+
|       EXPIRATION      |
|                       |
+-----+-----+-----+-----+
|      BLOCK COUNTER    |
+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
     </section>
     <section anchor="gnsrecords_edkey" numbered="true" toc="default">
       <name>EDKEY</name>
       <t>
         In GNS, a delegation of a label to a zone of type "EDKEY" is
         represented through a EDKEY record.
         The EDKEY DATA entry wire format
         is illustrated in <xref target="figure_edkeyrecord"/>.
       </t>
       <figure anchor="figure_edkeyrecord" title="The EDKEY DATA Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   PUBLIC KEY                  |
|                                               |
|                                               |
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>PUBLIC KEY</dt>
         <dd>
           A 256-bit EdDSA zone key.
         </dd>
       </dl>
         <t>
           For EDKEY zones the zone key material is derived using the
           curve parameters of the twisted edwards representation
           of Curve25519 <xref target="RFC7748" /> (a.k.a. Ed25519)
           with the Ed25519 scheme <xref target="ed25519" /> as specified in
           <xref target="RFC8032" />.
           The following naming convention is used for the
           cryptographic primitives of EDKEY zones:
         </t>
         <!-- Check if we want to use RFC8032 instead of paper ed25519 -->
         <dl>
           <dt>d</dt>
           <dd>
             is a 256-bit EdDSA private key.
           </dd>
           <dt>a</dt>
           <dd>
             is is an integer derived from d using the SHA-512 hash function
             as defined in <xref target="RFC8032" />.
           </dd>
           <dt>zk</dt>
           <dd>
             is the EdDSA public key corresponding to d. It is defined
             as the curve point a*G where G is the
             group generator of the elliptic curve
             as defined in <xref target="RFC8032" />.
           </dd>
           <dt>p</dt>
           <dd>
             is the prime of edwards25519 as defined in <xref target="RFC8032" />, i.e.
             2^255 - 19.
           </dd>
           <dt>G</dt>
           <dd>
             is the group generator (X(P),Y(P)) of edwards25519 as defined in
              <xref target="RFC8032" />.
           </dd>
           <dt>L</dt>
           <dd>
             is the order of the prime-order subgroup of edwards25519 in <xref target="RFC8032" />.
           </dd>
           <dt>KeyGen()</dt>
           <dd>
             The generation of the private key d and the associated public
             key zk := a*G where G is the
             group generator of the elliptic curve and a is an integer
             derived from d using the SHA-512 hash function
             as defined
             in Section 5.1.5 of <xref target="RFC8032" /> represents the KeyGen()
             function.
            </dd>
         </dl>
         <t>
           The zone type and zone key of an EDKEY are 4 + 32 bytes in length. This means that
           a zTLD will always fit into a single label and does
           not need any further conversion.
         </t>
         <t>
           The "EDKEY" ZKDF instantiation is based on <xref target="Tor224"/>.
           The calculation of a is defined in Section 5.1.5 of <xref target="RFC8032" />.
           Given a label, the output of the ZKDF function is
           calculated as follows:
         </t>
         <artwork name="" type="" align="left" alt=""><![CDATA[
ZKDF(zk,label):
  /* Calculate the blinding factor */
  PRK_h := HKDF-Extract ("key-derivation", zk)
  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
  /* Ensure that h == h mod L */
  h[31] &= 7

  zk' := h * zk
  return zk'
           ]]></artwork>
         <t>
           Implementers <bcp14>SHOULD</bcp14> employ a constant time scalar
           multiplication for the constructions above to protect against
           timing attacks. Otherwise, timing attacks could leak private key
           material if an attacker can predict when a system starts the
           publication process.
           <!--Also, implementers
           <bcp14>MUST</bcp14> ensure that the private key a is an ed25519 private key
           and specifically that "a[0] &#38; 7 == 0" holds.-->
         </t>
         <t>
           The EDKEY cryptosystem uses a
           hash-based key derivation function (HKDF) as defined in
           <xref target="RFC5869" />, using SHA-512 <xref target="RFC6234"/> for the extraction
           phase and HMAC-SHA256 <xref target="RFC6234"/> for the expansion phase.
           PRK_h is key material retrieved using an HKDF using the string
           "key-derivation" as salt and the zone key as initial
           keying material.
           The blinding factor h is the 512-bit HKDF expansion result.
           The expansion information input is
           a concatenation of the label and the string "gns".
           The result of the HKDF must be clamped and interpreted in network
           byte order.
           a is the 256-bit integer corresponding to the 256-bit private
           key d.
           The multiplication of zk with h is a point multiplication,
           while the division and multiplication of a and a1 with the
           co-factor are integer operations.
         </t>
         <t>
           The Sign(d,message) and Verify(zk,message,signature) procedures <bcp14>MUST</bcp14>
           be implemented as defined in <xref target="RFC8032" />.
         </t>
         <t>
           Signatures for EDKEY zones use a derived private scalar d'
           which is not compliant with <xref target="RFC8032" />.
           As the corresponding private key to the derived private scalar
           is not known, it is not possible to deterministically derive the
           signature part R according to <xref target="RFC8032" />.
           Instead, signatures <bcp14>MUST</bcp14> be generated as follows for any given
           message and private zone key:
           A nonce is calculated from the highest 32 bytes of the
           expansion of the private key d and the blinding factor h.
           The nonce is then hashed with the message to r.
           This way, the full derivation path is included in the calculation
           of the R value of the signature, ensuring that it is never reused
           for two different derivation paths or messages.
         </t>
         <artwork name="" type="" align="left" alt=""><![CDATA[
SignDerived(d,label,message):
  /* Key expansion */
  dh := SHA-512 (d)
  /* EdDSA clamping */
  a := dh[0..31]
  a[0] &= 248
  a[31] &= 127
  a[31] |= 64
  /* Calculate zk corresponding to d */
  zk := a * G

  /* Calculate blinding factor */
  PRK_h := HKDF-Extract ("key-derivation", zk)
  h := HKDF-Expand (PRK_h, label || "gns", 512 / 8)
  /* Ensure that h == h mod L */
  h[31] &= 7

  zk' := h * zk
  a1 := a >> 3
  a2 := (h * a1) mod L
  d' := a2 << 3
  nonce := SHA-256 (dh[32..63] || h)
  r := SHA-512 (nonce || message)
  R := r * G
  S := r + SHA-512(R || zk' || message) * d' mod L
  return (R,S)
           ]]></artwork>
         <t>
           A signature (R,S) is valid if the following holds:
         </t>
         <artwork name="" type="" align="left" alt=""><![CDATA[
VerifyDerived(zk,label,message,signature):
  zk' := ZKDF(zk,label)
  (R,S) := signature
  return S * G == R + SHA-512(R, zk', message) * zk'
           ]]></artwork>
         <t>
           The S-Encrypt() and S-Decrypt() functions use XSalsa20
           as defined in <xref target="XSalsa20" />
           (XSalsa20-Poly1305):
         </t>
         <artwork name="" type="" align="left" alt=""><![CDATA[
S-Encrypt(zk,label,expiration,message):
  PRK_k := HKDF-Extract ("gns-xsalsa-ctx-key", zk)
  PRK_n := HKDF-Extract ("gns-xsalsa-ctx-iv", zk)
  K := HKDF-Expand (PRK_k, label, 256 / 8)
  NONCE := HKDF-Expand (PRK_n, label, 128 / 8)
  IV := NONCE || expiration
  return XSalsa20-Poly1305(K, IV, message)

S-Decrypt(zk,label,expiration,ciphertext):
  PRK_k := HKDF-Extract ("gns-xsalsa-ctx-key", zk)
  PRK_n := HKDF-Extract ("gns-xsalsa-ctx-iv", zk)
  K := HKDF-Expand (PRK_k, label, 256 / 8)
  NONCE := HKDF-Expand (PRK_n, label, 128 / 8)
  IV := NONCE || expiration
  return XSalsa20-Poly1305(K, IV, ciphertext)
           ]]></artwork>
         <t>
           The result of the XSalsa20-Poly1305 encryption function is the encrypted
           ciphertext followed by the 128-bit authentication
           tag.
           Accordingly, the length of encrypted data equals the length of the
           data plus the 16 bytes of the authentication tag.
         </t>
         <t>
           The key K and counter IV are derived from
           the record label and the zone key zk using a hash-based key
           derivation function (HKDF) as defined in
           <xref target="RFC5869" />.
           SHA-512 <xref target="RFC6234"/> is used for the
           extraction phase and SHA-256 <xref target="RFC6234"/> for the expansion phase.
           The output keying material is 32 bytes (256 bits) for the symmetric
           key and 16 bytes (128 bits) for the NONCE.
           The symmetric key K is a 256-bit XSalsa20
           <xref target="XSalsa20" /> key.
           No additional authenticated data (AAD) is used.
         </t>
         <t>
           The nonce is combined with an 8 byte initialization vector.
           The initialization vector is the expiration time of the
           resource record block in network byte order.
           The resulting counter (IV) wire format is illustrated in
           <xref target="figure_hkdf_ivs_edkey"/>.
         </t>
         <figure anchor="figure_hkdf_ivs_edkey" title="The Counter Block Initialization Vector.">
           <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32
+-----+-----+-----+-----+
|         NONCE         |
|                       |
|                       |
|                       |
+-----+-----+-----+-----+
|       EXPIRATION      |
|                       |
+-----+-----+-----+-----+
             ]]></artwork>
       </figure>
     </section>
   </section>
   <section anchor="gnsrecords_redirect" numbered="true" toc="default">
     <name>Redirection Records</name>
     <t>
       Redirect records are used to redirect resolution.
       Any implementation <bcp14>SHOULD</bcp14> support all redirection record types defined here
       and <bcp14>MAY</bcp14> support any number of additional redirection records defined in
       the GNU Name System Record Types registry (see Section <xref target="gana"/>).
       Redirection records <bcp14>MUST</bcp14> have the CRITICAL flag set.
       Not supporting some record types can result in resolution failures.
       This can be a valid choice if some redirection record types have been
       determined to be insecure, or if an application has reasons to not
       support redirection to DNS for reasons such as complexity or security.
       Redirection records <bcp14>MUST NOT</bcp14> be stored and published under the apex label.
     </t>
     <section anchor="gnsrecords_rdr" numbered="true" toc="default">
       <name>REDIRECT</name>
       <t>
         A REDIRECT record is the GNS equivalent of a CNAME record in DNS.
         A REDIRECT record <bcp14>MUST</bcp14> be the only non-supplemental
         record under a label.
         There <bcp14>MAY</bcp14> be inactive records of the same type which have
         the SHADOW flag set in order to facilitate smooth changes of redirection
         targets.
         No other records are allowed.
         Details on processing of this record is defined in <xref target="redirect_processing"/>.

         A REDIRECT DATA entry is illustrated in <xref target="figure_redirectrecord"/>.
       </t>
       <figure anchor="figure_redirectrecord" title="The REDIRECT DATA Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   REDIRECT NAME               |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>REDIRECT NAME</dt>
         <dd>
           The name to continue with.
           The value of a redirect record can be a regular name, or a relative
           name.
           Relative GNS names are indicated by an extension label (U+002B, "+")
           as rightmost label.
           The string is UTF-8 encoded and 0-terminated.
         </dd>
       </dl>
     </section>
     <section anchor="gnsrecords_gns2dns" numbered="true" toc="default">
       <name>GNS2DNS</name>
       <t>
         It is possible to delegate a label back into DNS through a GNS2DNS record.
         The resource record contains a DNS name for the resolver to continue with
         in DNS followed by a DNS server. Both names are in the format defined in
         <xref target="RFC1034" /> for DNS names.
         There <bcp14>MAY</bcp14> be multiple GNS2DNS records under a label.
         There <bcp14>MAY</bcp14> also be DNSSEC DS records or any other records used to
         secure the connection with the DNS servers under the same label.
         There <bcp14>MAY</bcp14> be inactive records of the same type(s) which have
         the SHADOW flag set in order to facilitate smooth changes of redirection
         targets.
         No other non-supplemental record types are allowed in the same record set.
         A GNS2DNS DATA entry is illustrated in <xref target="figure_gns2dnsrecord"/>.</t>
       <figure anchor="figure_gns2dnsrecord" title="The GNS2DNS DATA Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      NAME                     |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                 DNS SERVER NAME               |
/                                               /
/                                               /
|                                               |
+-----------------------------------------------+
           ]]></artwork>
       </figure>
       <dl>
         <dt>NAME</dt>
         <dd>
           The name to continue with in DNS. The value is UTF-8 encoded and
           0-terminated.
         </dd>
         <dt>DNS SERVER NAME</dt>
         <dd>
           The DNS server to use. This value can be an IPv4 address in dotted-decimal
           form or an IPv6 address in colon-hexadecimal form or a DNS name.
           It can also be a relative GNS name ending with a
           "+" as the rightmost label.
           The implementation <bcp14>MUST</bcp14> check the string syntactically for
           an IP address in the respective notation before checking for a
           relative GNS name.
           If all three checks fail, the name <bcp14>MUST</bcp14> be treated as a DNS name.
           The value is UTF-8 encoded and 0-terminated.
         </dd>
       </dl>
       <t>
         NOTE: If an application uses DNS names obtained from GNS2DNS records
         in a DNS request they <bcp14>MUST</bcp14> first be converted to an IDNA compliant
         representation <xref target="RFC5890" />.
       </t>
     </section>
   </section>
   <section anchor="gnsrecords_other" numbered="true" toc="default">
       <name>Auxiliary Records</name>
       <t>
         This section defines the initial set of auxiliary GNS record types. Any
         implementation <bcp14>SHOULD</bcp14> be able to process the specified record types
         according to <xref target="record_processing"/>.
       </t>
     <section anchor="gnsrecords_leho" numbered="true" toc="default">
       <name>LEHO</name>
       <t>
         This record is used to provide a hint for LEgacy HOstnames:
         Applications can use the GNS to lookup IPv4 or IPv6 addresses of
         internet services.
         However, sometimes connecting to such services does not only require
         the knowledge of an address and port, but also requires the canonical
         DNS name of the service to be transmitted over the transport protocol.
         In GNS, legacy host name records provide applications the DNS name that
         is required to establish a connection to such a service.
         The most common use case is HTTP virtual hosting and TLS Server Name
         Indication <xref target="RFC6066"/>, where a DNS name must
         be supplied in the HTTP "Host"-header and the TLS handshake,
         respectively.
         Using a GNS name in those cases might not work as
         it might not be globally unique. Furthermore, even if uniqueness is
         not an issue, the legacy service might not even be aware of GNS.
       </t>
       <t>
         A LEHO resource record is expected to be found together in a single
         resource record with an IPv4 or IPv6 address.
           A LEHO DATA entry is illustrated in <xref target="figure_lehorecord"/>.
       </t>
       <figure anchor="figure_lehorecord" title="The LEHO DATA Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                 LEGACY HOSTNAME               |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>LEGACY HOSTNAME</dt>
         <dd>
           A UTF-8 string (which is not 0-terminated) representing the legacy hostname.
         </dd>
       </dl>
       <t>
         NOTE: If an application uses a LEHO value in an HTTP request header
         (e.g. "Host:" header) it <bcp14>MUST</bcp14> be converted to an IDNA compliant representation
         <xref target="RFC5890" />.
       </t>
     </section>
     <section anchor="gnsrecords_nick" numbered="true" toc="default">
       <name>NICK</name>
       <t>
         Nickname records can be used by zone administrators to publish a
         label that a zone prefers to have used when it is referred to.
         This is a suggestion to other zones what label to use when creating a
         delegation record (<xref target="gnsrecords_delegation" />) containing
         this zone key.
         This record <bcp14>SHOULD</bcp14> only be stored under the apex label "@" but <bcp14>MAY</bcp14> be
         returned with record sets under any label as a supplemental record.
         <xref target="nick_processing"/> details how a resolver must process
         supplemental and non-supplemental NICK records.
         A NICK DATA entry is illustrated in <xref target="figure_nickrecord"/>.
       </t>
       <figure anchor="figure_nickrecord" title="The NICK DATA Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                  NICKNAME                     |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>NICKNAME</dt>
         <dd>
           A UTF-8 string (which is not 0-terminated) representing the preferred
           label of the zone. This string <bcp14>MUST</bcp14> be a valid GNS label.
         </dd>
       </dl>
     </section>
     <section anchor="gnsrecords_box" numbered="true" toc="default">
       <name>BOX</name>
       <t>
         GNS lookups are expected to return all of the required useful
         information in one record set. This avoids unnecessary additional
         lookups and cryptographically ties together information that belongs
         together, making it impossible for an adversarial storage to provide
         partial answers that might omit information critical for security.
       </t>
       <t>
         This general strategy is incompatible with the
         special labels used by DNS for SRV and TLSA records.  Thus, GNS
         defines the BOX record format to box up SRV and TLSA records and
         include them in the record set of the label they are associated
         with.  For example, a
         TLSA record for "_https._tcp.example.org" will be stored in the record set of
         "example.org" as a BOX record with service (SVC) 443 (https) and protocol (PROTO) 6
         (tcp) and record TYPE "TLSA".
         For reference, see also <xref target="RFC2782" />.
           A BOX DATA entry is illustrated in <xref target="figure_boxrecord"/>.
       </t>
       <figure anchor="figure_boxrecord" title="The BOX DATA Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|   PROTO   |    SVC    |       TYPE            |
+-----------+-----------------------------------+
|                 RECORD DATA                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>PROTO</dt>
         <dd>
           the 16-bit protocol number, e.g. 6 for TCP.
           Note that values
           below 2^8 are reserved for 8-bit Internet Protocol numbers allocated by IANA <xref target="RFC5237" />.
           Values above 2^8 are allocated by the
           GNUnet Assigned Numbers Authority <xref target="GANA" />.
           In network byte order.
         </dd>
         <dt>SVC</dt>
         <dd>
           the 16-bit service value of the boxed record. In case of
           TCP and UDP it is the port number.
           In network byte order.
         </dd>
         <dt>TYPE</dt>
         <dd>
           is the 32-bit record type of the boxed record. In network byte order.
         </dd>
         <dt>RECORD DATA</dt>
         <dd>
           is a variable length field containing the "DATA" format of TYPE as
           defined for the respective TYPE in DNS.
         </dd>
       </dl>
     </section>
   </section>
   </section>
   <section anchor="publish" numbered="true" toc="default">
     <name>Record Encoding</name>
     <t>
       Any API which allows storing a value under a 512-bit key and retrieving
       one or more values from the key can be used by an implementation for record storage.
       To be useful, the API <bcp14>MUST</bcp14> permit storing at least 176 byte values
       to be able to support the defined zone delegation record encodings,
       and <bcp14>SHOULD</bcp14> allow at least 1024 byte values.
       In the following, it is assumed that an implementation realizes two
       procedures on top of a storage:
     </t>
     <artwork name="" type="" align="left" alt=""><![CDATA[
PUT(key,value)
GET(key) -> value
       ]]></artwork>
     <t>
       There is no explicit delete function as the deletion of a non-expired
       record would require a revocation of the record.
       In GNS, zones can only be revoked as a whole. Records automatically
       expire and it is under the discretion of the storage as to when to delete
       the record. The GNS implementation <bcp14>MUST NOT</bcp14> publish expired resource
       records. Any GNS resolver <bcp14>MUST</bcp14> discard expired records returned from
       the storage.
     </t>
     <t>
       Resource records are grouped by their respective labels,
       encrypted and published together in a single resource records block
       (RRBLOCK) in the storage under a key q as illustrated in <xref target="figure_storage_publish"/>.
       The key q is derived from the zone key and the respective
       label of the contained records.
       The required knowledge of both zone key and label in combination
       with the similarly derived symmetric secret keys and blinded zone keys
       ensure query privacy (see <xref target="RFC8324"/>, Section 3.5).
       The storage key derivation and records
       block creation is specified in the following sections.
       The implementation <bcp14>MUST</bcp14> use the PUT storage procedure in order to update
       the zone contents accordingly.
     </t>
     <figure anchor="figure_storage_publish" title="Management and publication of local zones in the distributed storage.">
       <artwork name="" type="" align="left" alt=""><![CDATA[
                           Local Host          |   Remote
                                               |   Storage
                                               |
                                               |    +---------+
                                               |   /         /|
                                               |  +---------+ |
+-----------+                                  |  |         | |
|           |       +---------+PUT(q, RRBLOCK) |  | Record  | |
|    User   |       |  Zone   |----------------|->| Storage | |
|           |       | Master  |                |  |         |/
+-----------+       +---------+                |  +---------+
     |                     A                   |
     |                     | Zone records      |
     |                     | grouped by label  |
     |                     |                   |
     |                 +---------+             |
     |Create / Delete /    |    /|             |
     |and Update     +---------+ |             |
     |Local Zones    |         | |             |
     |               |  Local  | |             |
     +-------------->|  Zones  | |             |
                     |         |/              |
                     +---------+               |
         ]]></artwork>
     </figure>

     <section anchor="blinding" numbered="true" toc="default">
       <name>The Storage Key</name>
       <t>
         Given a label, the storage key q is derived as follows:
       </t>
       <artwork name="" type="" align="left" alt=""><![CDATA[
q := SHA-512 (ZKDF(zk, label))
         ]]></artwork>
       <dl>
         <dt>label</dt>
         <dd>is a UTF-8 string under which the resource records are published.
         </dd>
         <dt>zk</dt>
         <dd>
           is the zone key.
         </dd>
         <dt>q</dt>
         <dd>
           Is the 512-bit storage key under which the resource records block is
           published.
           It is the SHA-512 hash <xref target="RFC6234"/> over the derived zone key.
         </dd>
       </dl>
     </section>
     <section anchor="records_block" numbered="true" toc="default">
       <name>The Records Block</name>
       <t>
         GNS records are grouped by their labels and published as a single
         block in the storage. The grouped record sets <bcp14>MAY</bcp14> be paired with any
         number of supplemental records. Supplemental records <bcp14>MUST</bcp14> have the
         supplemental flag set (See <xref target="rrecords"/>).
         The contained resource records are encrypted using a symmetric
         encryption scheme.
         A GNS implementation publishes RRBLOCKs
         in accordance to the properties and recommendations of the underlying
         storage. This can include a periodic refresh operation to ensure the
         availability of the published RRBLOCKs.
         The GNS RRBLOCK wire format is illustrated in
         <xref target="figure_record_block"/>.
       </t>
       <figure anchor="figure_record_block" title="The RRBLOCK Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|          SIZE         |    ZONE TYPE          |
+-----+-----+-----+-----+-----+-----+-----+-----+
/                  ZONE KEY                     /
/                  (BLINDED)                    /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   SIGNATURE                   |
/                                               /
/                                               /
|                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                    BDATA                      /
/                                               /
/                                               |
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>SIZE</dt>
         <dd>
           A 32-bit value containing the length of the block in bytes.
           In network byte order.
           While a 32-bit value is used,
           implementations <bcp14>MAY</bcp14> refuse to publish blocks beyond a certain
           size significantly below 4 GB.
         </dd>
         <dt>ZONE TYPE</dt>
         <dd>
           is the 32-bit ztype. In network byte order.
         </dd>
         <dt>ZONE KEY</dt>
         <dd>
           is the blinded zone key "ZKDF(zk, label)"
           to be used to verify SIGNATURE.
           The length and format of the public key depends on the ztype.
         </dd>
         <dt>SIGNATURE</dt>
         <dd>
           The signature is computed over the EXPIRATION and BDATA fields
           as detailed in <xref target="figure_rrsigwithpseudo"/>.
           The length and format of the signature depends on the ztype.
           The signature is created using the SignDerived() function of
           the cryptosystem of the zone (see <xref target="zones" />).
         </dd>
         <dt>EXPIRATION</dt>
         <dd>
           Specifies when the RRBLOCK expires and the encrypted block
           <bcp14>SHOULD</bcp14> be removed from the storage and caches as it is likely stale.
           However, applications <bcp14>MAY</bcp14> continue to use non-expired individual
           records until they expire.  The value <bcp14>MUST</bcp14> be set to the
           expiration time of the resource record contained within this block with the
           smallest expiration time.
           If a records block includes shadow records, then the maximum
           expiration time of all shadow records with matching type and the
           expiration times of the non-shadow records is considered.
           This is a 64-bit absolute date in microseconds since midnight
           (0 hour), January 1, 1970 UTC in network byte order.
         </dd>
         <dt>BDATA</dt>
         <dd>
           The encrypted RDATA. Its size is determined by the S-Encrypt()
           function of the ztype.
         </dd>
       </dl>
       <t>
         The signature over the public key covers a 32-bit pseudo header
         conceptually prefixed to the EXPIRATION and the BDATA fields.
         The wire format is illustrated
         in <xref target="figure_rrsigwithpseudo"/>.
       </t>
       <figure anchor="figure_rrsigwithpseudo" title="The Wire Format used for creating the signature of the RRBLOCK.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|         SIZE          |       PURPOSE (0x0F)  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                    BDATA                      |
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
           ]]></artwork>
       </figure>
       <dl>
         <dt>SIZE</dt>
         <dd>
           A 32-bit value containing the length of the signed data in bytes
           in network byte order.
         </dd>
         <dt>PURPOSE</dt>
         <dd>
           A 32-bit signature purpose flag. The value of this
           field <bcp14>MUST</bcp14> be 15.
           The value is encoded in network byte order.
           It defines the context in which
           the signature is created so that it cannot be reused in other parts
           of the protocol including possible future extensions.
           The value of this field corresponds to an entry in the
           GANA "GNUnet Signature Purpose" registry <xref target="gana"/>.
         </dd>
         <dt>EXPIRATION</dt>
         <dd>
           Field as defined in the RRBLOCK message above.
         </dd>
         <dt>BDATA</dt>
         <dd>Field as defined in the RRBLOCK message above.</dd>
       </dl>

       <t>
         A symmetric encryption scheme is used to encrypt the resource records
         set RDATA into the BDATA field of a GNS RRBLOCK.
         The wire format of the RDATA is illustrated in
         <xref target="figure_rdata"/>.
       </t>
       <figure anchor="figure_rdata" title="The RDATA Wire Format.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
0     8     16    24    32    40    48    56
+-----+-----+-----+-----+-----+-----+-----+-----+
|                 EXPIRATION                    |
+-----+-----+-----+-----+-----+-----+-----+-----+
|    SIZE   |    FLAGS  |        TYPE           |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                      DATA                     /
/                                               /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
|                   EXPIRATION                  |
+-----+-----+-----+-----+-----+-----+-----+-----+
|    SIZE   |    FLAGS  |        TYPE           |
+-----+-----+-----+-----+-----+-----+-----+-----+
|                     DATA                      /
/                                               /
+-----+-----+-----+-----+-----+-----+-----+-----+
/                     PADDING                   /
/                                               /
           ]]></artwork>
       </figure>
       <dl>
         <dt>EXPIRATION, SIZE, TYPE, FLAGS and DATA</dt>
         <dd>
           These fields were defined
           in the resource record format in <xref target="rrecords" />.
         </dd>
         <dt>PADDING</dt>
         <dd>
           When publishing an RDATA block, the implementation <bcp14>MUST</bcp14> ensure that
           the size of the RDATA is a power of two
           using the padding field. The field <bcp14>MUST</bcp14> be set to zero and <bcp14>MUST</bcp14> be
           ignored on receipt.
           As a special exception, record sets with (only) a zone delegation
           record type are never padded.
           Note that a record set with a delegation record <bcp14>MUST NOT</bcp14>
           contain other records. If other records are encountered, the whole
           record block <bcp14>MUST</bcp14> be discarded.
         </dd>
       </dl>
     </section>
   </section>
    <section anchor="resolution" numbered="true" toc="default">
     <name>Name Resolution</name>
     <t>
       Names in GNS are resolved by recursively querying the record storage.
       Recursive in this context means that a resolver does not provide
       intermediate results for a query to the application.
       Instead, it <bcp14>MUST</bcp14> respond to a resolution request with either the
       requested resource record or an error message in case the resolution
       fails.
       <xref target="figure_resolution"/> illustrates how an application
       requests the lookup of a GNS name (1).
       The application <bcp14>MAY</bcp14> provide a desired record type to the resolver.
       Subsequently, the Start Zone is determined (2) and the recursive
       resolution process started.
       This is where the desired record type is used to guide processing.
       For example, if a zone delegation record type is requested, the
       resolution of the apex label in that zone must be skipped, as
       the desired record is already found.
       Details on how the resolution process is initiated and each iterative
       result (3a,3b) in the resolution is processed are provided in the sections below.
       The results of the lookup are eventually returned to the application (4).
       The implementation <bcp14>MUST NOT</bcp14> filter results
       according to the desired record type.
       Filtering of record sets is typically done by the application.
     </t>
     <figure anchor="figure_resolution" title="The recursive GNS resolution process.">
       <artwork name="" type="" align="left" alt=""><![CDATA[
                           Local Host             |   Remote
                                                  |   Storage
                                                  |
                                                  |    +---------+
                                                  |   /         /|
                                                  |  +---------+ |
+-----------+ (1) Name +----------+               |  |         | |
|           | Lookup   |          | (3a) GET(q)   |  | Record  | |
|Application|----------| Resolver |---------------|->| Storage | |
|           |<---------|          |<--------------|--|         |/
+-----------+ (4)      +----------+ (3b) RRBLOCK  |  +---------+
              Records     A                       |
                          |                       |
     (2) Determination of |                       |
         Start Zone       |                       |
                          |                       |
                       +---------+                |
                      /   |     /|                |
                     +---------+ |                |
                     |         | |                |
                     |  Start  | |                |
                     |  Zones  | |                |
                     |         |/                 |
                     +---------+                  |
         ]]></artwork>
     </figure>
     <section anchor="governance" numbered="true" toc="default">
       <name>Start Zones</name>
       <t>
         The resolution of a GNS name starts by identifying the start zone
         suffix. Once the start zone suffix is identified, recursive resolution
         of the remainder of the name is initiated (<xref target="recursion"/>).
         There are two types of start zone suffixes: zTLDs and local
         suffix-to-zone mappings.
         The choice of available suffix-to-zone mappings is at the sole
         discretion of the local system administrator or user.
         This property addresses the issue of a single hierarchy with a
         centrally controlled root and the related issue of distribution and
         management of root servers in DNS (see <xref target="RFC8324"/>, Section 3.10 and 3.12).
       </t>
       <t>
         For names ending with a zTLD the start zone is explicitly given in the
         suffix of the name to resolve.
         In order to ensure uniqueness of names with zTLDs any
         implementation <bcp14>MUST</bcp14> use the given zone as start zone.
         An implementation <bcp14>MUST</bcp14> first try to interpret the rightmost label of
         the given name as the beginning of a zTLD (<xref target="zTLD"/>).
         If the rightmost label cannot be (partially) decoded or if it does not
         indicate a supported ztype, the name is treated as a normal name and
         start zone discovery <bcp14>MUST</bcp14> continue with finding a local suffix-to-zone
         mapping.
         If a valid ztype can be found in the rightmost label, the
         implementation <bcp14>MUST</bcp14> try to synthesize and decode the zTLD to retrieve
         the start zone key according to <xref target="zTLD"/>.
         If the zTLD cannot be synthesized or decoded, the resolution of
         the name fails and an error is returned to the application.
         Otherwise, the zone key <bcp14>MUST</bcp14> be used as the start zone:
       </t>
       <artwork name="" type="" align="left" alt=""><![CDATA[
Example name: www.example.<zTLD>
=> Start zone: zk of type ztype
=> Name to resolve from start zone: www.example
         ]]></artwork>
       <t>
         For names not ending with a zTLD the resolver <bcp14>MUST</bcp14> determine the start
         zone through a local suffix-to-zone mapping.
         Suffix-to-zone mappings <bcp14>MUST</bcp14> be configurable through a local
         configuration file or database by the user or system administrator.
         A suffix <bcp14>MAY</bcp14> consist of multiple GNS labels concatenated with a
         label separator.
         If multiple suffixes match the name to resolve, the longest
         matching suffix <bcp14>MUST</bcp14> be used. The suffix length of two results
         <bcp14>MUST NOT</bcp14> be equal. This indicates a misconfiguration and the
         implementation <bcp14>MUST</bcp14> return an error.
         The following is a non-normative example mapping of start zones:
       </t>
       <artwork name="" type="" align="left" alt=""><![CDATA[
Example name: www.example.org
Local suffix mappings:
org = zTLD0 := Base32GNS(ztype0||zk0)
example.org = zTLD1 := Base32GNS(ztype1||zk1)
example.com = zTLD2 := Base32GNS(ztype2||zk2)
...
=> Start zone: zk1
=> Name to resolve from start zone: www
         ]]></artwork>
       <t>
         The process given above <bcp14>MAY</bcp14> be supplemented with other mechanisms if
         the particular application requires a different process.
         If no start zone can be discovered, resolution <bcp14>MUST</bcp14> fail and an
         error <bcp14>MUST</bcp14> be returned to the application.
       </t>
     </section>
       <section anchor="recursion" numbered="true" toc="default">
         <name>Recursion</name>
         <t>
           In each step of the recursive name resolution, there is an
           authoritative zone zk and a name to resolve.
           The name <bcp14>MAY</bcp14> be empty.
           If the name is empty, it is interpreted as the apex label "@".
           Initially, the authoritative zone is the start zone.
         </t>
         <t>
           From here, the following steps are recursively executed, in order:
         </t>
         <ol>
           <li>Extract the right-most label from the name to look up.</li>
           <li>Calculate q using the label and zk as defined in
           <xref target="blinding" />.</li>
           <li>Perform a storage query GET(q) to retrieve the RRBLOCK.</li>
           <li>Verify and process the RRBLOCK and decrypt the BDATA contained
             in it as defined in <xref target="records_block" />.</li>
         </ol>
         <t>
           Upon receiving the RRBLOCK from the storage, as part of verifying the
           provided signature, the resolver <bcp14>MUST</bcp14> check that the SHA-512 hash of the
           derived authoritative zone key zk' from the RRBLOCK matches the query q
           and that the block is not yet expired.
           If the signature does not match or the block is expired, the RRBLOCK <bcp14>MUST</bcp14>
           be ignored and, if applicable, the storage lookup GET(q) <bcp14>MUST</bcp14> continue to
           look for other RRBLOCKs.
         </t>
       </section>
       <section anchor="record_processing" numbered="true" toc="default">
         <name>Record Processing</name>
         <t>
           Record processing occurs once a well-formed block has been decrypted.
           In record processing, only the valid records obtained are considered.
           To filter records by validity, the resolver
           <bcp14>MUST</bcp14> at least check the expiration time and the FLAGS field of the
           respective record.  In particular, SHADOW and
           SUPPLEMENTAL flags can exclude the record from being considered.
           If the resolver encounters a record with the CRITICAL flag set and
           does not support the record type the resolution <bcp14>MUST</bcp14> be aborted
           and an error <bcp14>MUST</bcp14> be returned. The information that the critical
           record could not be processed <bcp14>SHOULD</bcp14> be returned in the error
           description. The implementation <bcp14>MAY</bcp14> choose not to return the reason for the failure,
           merely complicating troubleshooting for the user.
         </t>
         <t>
           The next steps depend on the context of the name that is being
           resolved:
         </t>
         <ul>
         <li>
           Case 1:
           If the filtered record set consists of a single REDIRECT record,
           the remainder of the name is prepended to the REDIRECT data and the
           recursion is started again from the resulting name.
           Details are described in <xref target="redirect_processing" />.
         </li>
         <li>
           Case 2:
           If the filtered record set consists exclusively of one or more GNS2DNS records
           resolution continues with DNS.
           Details are described in <xref target="gns2dns_processing" />.
         </li>
         <li>
           Case 3:
           If the remainder of the name to be resolved is of the format
           "_SERVICE._PROTO" and the record set contains one or more matching BOX
           records, the records in the BOX records are the final result and the recursion
           is concluded as described in <xref target="box_processing" />.
         </li>
         <li>
           Case 4:
           If the current record set
           consist of a single delegation record,
           resolution of the remainder of the name is delegated to
           the target zone as described in <xref target="delegation_processing" />.
         </li>
         <li>
           Case 5:
           If the remainder of the name to resolve is empty
           the record set is the final result.
           If any NICK records are in the final result set, it <bcp14>MUST</bcp14> be
           processed according to <xref target="nick_processing" />.
           Otherwise, the final result set is returned.
         </li>
         <li>
           Finally, if none of the above is applicable resolution fails and the
           resolver <bcp14>MUST</bcp14> return an empty record set.
         </li>
        </ul>
         <section anchor="redirect_processing" numbered="true" toc="default">
           <name>REDIRECT</name>
           <t>
             If the remaining name is empty and the desired record type is
             REDIRECT, in which case the resolution concludes with the REDIRECT record.
             If the rightmost label of the redirect name is the extension label
             (U+002B, "+"),
             resolution continues in GNS with the new name in the
             current zone.
             Otherwise, the resulting name is resolved via the
             default operating system name resolution process.
             This can in turn trigger a GNS name resolution process depending
             on the system configuration.
             In case resolution continues in DNS, the name <bcp14>MUST</bcp14> first be
             converted to an IDNA compliant representation <xref target="RFC5890" />.
           </t>
           <t>
             In order to prevent infinite loops, the resolver <bcp14>MUST</bcp14>
             implement loop detection or limit the number of recursive
             resolution steps.
             The loop detection <bcp14>MUST</bcp14> be effective even
             if a REDIRECT found in GNS triggers subsequent GNS lookups via
             the default operating system name resolution process.
           </t>
         </section>
         <section anchor="gns2dns_processing" numbered="true" toc="default">
           <name>GNS2DNS</name>
           <t>
             When a resolver encounters one or more GNS2DNS records and the remaining name
             is empty and the desired record type is GNS2DNS, the GNS2DNS
             records are returned.
           </t>
           <t>
             Otherwise, it is expected that the resolver first resolves the
             IP addresses of the specified DNS name servers.
             The DNS name <bcp14>MUST</bcp14> be converted to an IDNA compliant
             representation <xref target="RFC5890" /> for resolution in DNS.
             GNS2DNS records <bcp14>MAY</bcp14>
             contain numeric IPv4 or IPv6 addresses, allowing the resolver to
             skip this step.
             The DNS server names might themselves be names in GNS or DNS.
             If the rightmost label of the DNS server name is the extension label
             (U+002B, "+"), the rest of the name is to be
             interpreted relative to the zone of the GNS2DNS record.
             If the DNS server name ends in a label representation of a
             zone key, the DNS server name is to be resolved against
             the GNS zone zk.
           </t>
           <t>
             Multiple GNS2DNS records can be stored under the same label,
             in which case the resolver <bcp14>MUST</bcp14> try all of them.
             The resolver <bcp14>MAY</bcp14> try them in any order or even in parallel.
             If multiple GNS2DNS records are present, the DNS name <bcp14>MUST</bcp14> be
             identical for all of them. Otherwise, it is not clear which name
             the resolver is supposed to follow. If multiple DNS names are
             present the resolution fails and an
             appropriate error is <bcp14>SHOULD</bcp14> be returned to the application.
           </t>
           <t>
             If there are DNSSEC DS records or any other records used to
             secure the connection with the DNS servers stored under the label,
             the DNS resolver <bcp14>SHOULD</bcp14> use them to secure the connection with
             the DNS server.
           </t>
           <t>
             Once the IP addresses of the DNS servers have been determined,
             the DNS name from the GNS2DNS record is appended
             to the remainder of the name to be resolved, and
             resolved by querying the DNS name server(s).
             The synthesized name has to be converted to an IDNA compliant
             representation <xref target="RFC5890" /> for resolution in DNS.
             If such a conversion is not possible, the resolution <bcp14>MUST</bcp14> be aborted
             and an error <bcp14>MUST</bcp14> be returned. The information that the critical
             record could not be processed <bcp14>SHOULD</bcp14> be returned in the error
             description. The implementation <bcp14>MAY</bcp14> choose not to return the reason for the failure,
             merely complicating troubleshooting for the user.
           </t>
           <t>
             As the DNS servers
             specified are possibly authoritative DNS servers, the GNS resolver <bcp14>MUST</bcp14>
             support recursive DNS resolution and <bcp14>MUST NOT</bcp14> delegate this to the
             authoritative DNS servers.
             The first successful recursive name resolution result
             is returned to the application.
             In addition, the resolver <bcp14>SHOULD</bcp14> return the queried DNS name as a
             supplemental LEHO record (see <xref target="gnsrecords_leho" />) with a
             relative expiration time of one hour.
           </t>
           <t>
             Once the transition from GNS into DNS is made through a
             GNS2DNS record, there is no "going back".
             The (possibly recursive) resolution of the DNS name <bcp14>MUST NOT</bcp14>
             delegate back into GNS and should only follow the DNS specifications.
             For example, names contained in DNS CNAME records <bcp14>MUST NOT</bcp14> be
             interpreted by resolvers that support both DNS and GNS as GNS names.
           </t>
           <t>
             GNS resolvers <bcp14>SHOULD</bcp14> offer a configuration
             option to disable DNS processing to avoid information leakage
             and provide a consistent security profile for all name resolutions.
             Such resolvers would return an empty record set upon encountering
             a GNS2DNS record during the recursion. However, if GNS2DNS records
             are encountered in the record set for the apex label and a GNS2DNS record
             is explicitly requested by the application, such records <bcp14>MUST</bcp14>
             still be returned, even if DNS support is disabled by the
             GNS resolver configuration.
           </t>
           <!-- FIXME: State the DNS resolution never "returns" to GNS. -->
         </section>
         <section anchor="box_processing" numbered="true" toc="default">
           <name>BOX</name>
           <t>
             When a BOX record is received, a GNS resolver must unbox it if the
             name to be resolved continues with "_SERVICE._PROTO".
             Otherwise, the BOX record is to be left untouched. This way, TLSA
             (and SRV) records do not require a separate network request, and
             TLSA records become inseparable from the corresponding address
             records.
           </t>
         </section>
         <section anchor="delegation_processing" numbered="true" toc="default">
           <name>Zone Delegation Records</name>
           <t>
             When the resolver encounters a record of a supported
             zone delegation record type (such as PKEY or EDKEY)
             and the remainder of the name is not empty, resolution continues
             recursively with the remainder of the name in the
             GNS zone specified in the delegation record.
           </t>
           <t>
             Whenever a resolver encounters a new GNS zone, it <bcp14>MUST</bcp14>
             check against the local revocation list whether the respective
             zone key has been revoked. If the zone key was revoked, the
             resolution <bcp14>MUST</bcp14> fail with an empty result set.
           </t>
           <t>
             Implementations <bcp14>MUST NOT</bcp14> allow multiple different zone
             delegations under a single label.
             Implementations <bcp14>MAY</bcp14> support any subset of ztypes.
             Handling of
             Implementations <bcp14>MUST NOT</bcp14> process zone delegation for the apex
             label "@". Upon encountering a zone delegation record under
             this label, resolution fails and an error <bcp14>MUST</bcp14> be returned. The
             implementation <bcp14>MAY</bcp14> choose not to return the reason for the failure,
             merely impacting troubleshooting information for the user.
           </t>
           <t>
             If the remainder of the name to resolve is empty and a record set
             was received containing only a single delegation record, the
             recursion is continued with the record value as authoritative zone
             and the apex label "@" as remaining name.
             Except in the case where the desired record type as specified by
             the application is equal to the ztype, in which case the delegation
             record is returned.
           </t>
         </section>
         <section anchor="nick_processing" numbered="true" toc="default">
           <name>NICK</name>
           <t>
             NICK records are only relevant to the recursive resolver
             if the record set in question is the final result which is to
             be returned to the application. The encountered NICK records can either
             be supplemental (see <xref target="rrecords"/>) or
             non-supplemental.
             If the NICK record is supplemental, the resolver only returns the
             record set if one of the non-supplemental records matches the
             queried record type.
             It is possible that one record set contains both supplemental
             and non-supplemental NICK records.
           </t>
           <t>
             The differentiation between a supplemental and non-supplemental
             NICK record allows the application to match the record to the
             authoritative zone. Consider the following example:
           </t>
         <artwork name="" type="" align="left" alt=""><![CDATA[
Query: alice.example (type=A)
Result:
A: 192.0.2.1
NICK: eve (non-Supplemental)
         ]]></artwork>
        <t>
          In this example, the returned NICK record is non-supplemental.
          For the application, this means that the NICK belongs to the zone
          "alice.example" and is published under the apex label along with an A
          record. The NICK record is interpreted as: The zone defined by
          "alice.example" wants to be referred to as "eve".
          In contrast, consider the following:
        </t>
         <artwork name="" type="" align="left" alt=""><![CDATA[
Query: alice.example (type=AAAA)
Result:
AAAA: 2001:DB8::1
NICK: john (Supplemental)
         ]]></artwork>
     <t>
       In this case, the NICK record is marked as supplemental. This means that
       the NICK record belongs to the zone "example" and is published under the
       label "alice" along with an A record. The NICK record should be
       interpreted as: The zone defined by "example" wants to be referred to as
       "john". This distinction is likely useful for other records published as
       supplemental.
      </t>


         </section>
       </section>
     </section>
     <section anchor="encoding" numbered="true" toc="default">
       <name>Internationalization and Character Encoding</name>
       <t>
         All names in GNS are encoded in UTF-8 <xref target="RFC3629" />.
         Labels <bcp14>MUST</bcp14> be canonicalized using
         Normalization Form C (NFC) <xref target="Unicode-UAX15"/>.
         This does not include any DNS names found in DNS records, such as CNAME
         record data, which is internationalized through the IDNA specifications
         <xref target="RFC5890" />.
       </t>
     </section>
     <section anchor="security" numbered="true" toc="default">
       <name>Security and Privacy Considerations</name>
       <section anchor="security_availability" numbered="true" toc="default">
         <name>Availability</name>
         <t>
           In order to ensure availability of records beyond their
           absolute expiration times, implementations <bcp14>MAY</bcp14> allow to locally
           define relative expiration time values of records.
           Records can then be published recurringly with updated
           absolute expiration times by the implementation.
         </t>
         <t>
           Implementations <bcp14>MAY</bcp14> allow users to manage private records in
           their zones that are not published in the storage.
           Private records are considered just like
           regular records when resolving labels in local zones,
           but their data is completely unavailable to non-local users.
         </t>
       </section>
       <section anchor="security_agility" numbered="true" toc="default">
         <name>Agility</name>
         <t>
           The security of cryptographic systems depends on both the strength of
           the cryptographic algorithms chosen and the strength of the keys used
           with those algorithms.  The security also depends on the engineering
           of the protocol used by the system to ensure that there are no
           non-cryptographic ways to bypass the security of the overall system.
           This is why developers of applications managing GNS zones <bcp14>SHOULD</bcp14>
           select a default ztype considered secure at the time of
           releasing the software.
           For applications targeting end users that are not expected to
           understand cryptography, the application developer <bcp14>MUST NOT</bcp14> leave
           the ztype selection of new zones to end users.
         </t>
         <t>
           This document concerns itself with the selection of cryptographic
           algorithms used in GNS.
           The algorithms identified in this document are not known to be
           broken (in the cryptographic sense) at the current time, and
           cryptographic research so far leads us to believe that they are
           likely to remain secure into the foreseeable future.  However, this
           is not necessarily forever, and it is expected that new revisions of
           this document will be issued from time to time to reflect the current
           best practices in this area.
         </t>
         <t>
           In terms of crypto-agility, whenever the need for an updated cryptographic
           scheme arises to, for example, replace ECDSA over Ed25519 for
           PKEY records it can simply be introduced
           through a new record type.
           Zone administrators can then replace
           the delegation record type for future records.
           The old record type remains
           and zones can iteratively migrate to the updated zone keys.
           To ensure that implementations correctly generate an error message
           when encountering a ztype that they do not support,
           current and future delegation records must always have the
           CRITICAL flag set.
         </t>
       </section>
       <section anchor="security_cryptography" numbered="true" toc="default">
         <name>Cryptography</name>
         <t>
           The following considerations provide background on the design choices
           of the ztypes specified in this document.
           When specifying new ztypes as per <xref target="zones"/>, the same
           considerations apply.
         </t>
         <t>
           GNS PKEY zone keys use ECDSA over Ed25519.
           This is an unconventional choice,
           as ECDSA is usually used with other curves.  However, standardized
           ECDSA curves are problematic for a range of reasons described in
           the Curve25519 and EdDSA papers <xref target="ed25519"/>.
           Using EdDSA directly is also
           not possible, as a hash function is used on the private key which
           destroys the linearity that the key blinding in GNS depends upon.
           We are not aware of anyone suggesting that using Ed25519 instead
           of another common curve of similar size would lower the security of
           ECDSA.  GNS uses 256-bit curves because that way the encoded (public)
           keys fit into a single DNS label, which is good for usability.
         </t>
         <t>
           In order to ensure ciphertext indistinguishability, care must be
           taken with respect to the initialization vector in the counter
           block. In our design, the IV always includes the expiration time of the
           record block.
           When applications store records with relative expiration times,
           monotonicity is implicitly
           ensured because each time a block is published into the storage, its IV is
           unique as the expiration time is calculated dynamically and increases
           monotonically with the system time. Still,
           an implementation <bcp14>MUST</bcp14> ensure that when relative expiration times
           are decreased, the expiration time of the next record block <bcp14>MUST</bcp14>
           be after the last published block.
           For records where an absolute expiration time is used, the implementation
           <bcp14>MUST</bcp14> ensure that the expiration time is always increased when the record
           data changes. For example, the expiration time on the wire could be increased
           by a single microsecond even if the user did not request a change.
           In case of deletion of all resource records under a label, the
           implementation <bcp14>MUST</bcp14> keep track of the last absolute expiration time
           of the last published resource block.  Implementations <bcp14>MAY</bcp14> define 
           and use a special record type as a tombstone that preserves the last
           absolute expiration time, but then <bcp14>MUST</bcp14> take care to not publish a
           block with this record.
           When new records are added under this label later, the implementation
           <bcp14>MUST</bcp14> ensure that the expiration times are after the last published
           block.
           Finally, in order to ensure monotonically increasing expiration times
           the implementation <bcp14>MUST</bcp14> keep a local record of the last time obtained
           from the system clock, so as to construct a monotonic clock in case
           the system clock jumps backwards.
         </t>
       </section>
       <section anchor="security_abuse" numbered="true" toc="default">
         <name>Abuse Mitigation</name>
         <t>
           GNS names are UTF-8 strings. Consequently, GNS faces similar issues
           with respect to name spoofing as DNS does for internationalized
           domain names.
           In DNS, attackers can register similar sounding or looking
           names (see above) in order to execute phishing attacks.
           GNS zone administrators must take into account this attack vector and
           incorporate rules in order to mitigate it.
         </t>
         <t>
           Further, DNS can be used to combat illegal content on the internet
           by having the respective domains seized by authorities.
           However, the same mechanisms can also be abused in order to impose
           state censorship, which is one of the motivations behind GNS.
           In GNS, TLDs are not enumerable. By design, the start zone of
           the resolver is defined locally and hence such a seizure is
           difficult and ineffective in GNS.
           <!--In particular, GNS does not support WHOIS (<xref target="RFC3912" />).-->
         </t>
       </section>
       <section anchor="security_keymanagement" numbered="true" toc="default">
         <name>Zone Management</name>
         <t>
           In GNS, zone administrators need to manage and protect their zone
           keys. Once a zone key is lost, it cannot be recovered or revoked.
           Revocation messages can be pre-calculated if revocation is
           required in case a zone key is lost.
           Zone administrators, and for GNS this includes end-users, are
           required to responsibly and diligently protect their cryptographic
           keys.
           GNS supports signing records in advance ("offline") in order to
           support processes which aim to protect private keys such as air gaps.
           <!-- It does not support separate zone signing and key-signing keys
           (as in <xref target="RFC6781" />) in order to provide usable security. This is not useful for any implementer -->
         </t>
         <t>
           Similarly, users are required to manage their local start zone configuration.
           In order to ensure integrity and availability or names, users must
           ensure that their local start zone information is not compromised or
           outdated.
           It can be expected that the processing of zone revocations and an
           initial start zone is provided with a GNS implementation
           ("drop shipping").
           Shipping an initial start zone configuration effectively establishes
           a root zone.
           Extension and customization of the zone is at the full discretion of
           the user.
         </t>
         <t>
           While implementations following this specification will be
           interoperable, if two implementations connect to different storages
           they are mutually unreachable.
           This can lead to a state where a record exists in the global
           namespace for a particular name, but the implementation is not
           communicating with the storage and is hence unable to resolve it.
           This situation is similar to a split-horizon DNS configuration.
           Which storages are implemented usually depends on the application
           it is built for.
           The storage used will most likely depend on the specific application
           context using GNS resolution.
           For example, one application is the resolution of hidden services
           within the Tor network, which would suggest using Tor routers for storage.
           <!-- FIXME: add non-normative reference to Tor / Tor hidden services here? -->
           Implementations of "aggregated" storages are conceivable, but
           are expected to be the exception.
         </t>
       </section>
       <section anchor="security_dht" numbered="true" toc="default">
         <name>DHTs as Storage</name>
         <t>
           This document does not specify the properties of the underlying
           storage which is required by any GNS implementation.
           It is important to note that the properties of the underlying
           storage are directly inherited by the
           GNS implementation. This includes both security as well as
           other non-functional properties such as scalability and performance.
           Implementers should take great care when selecting or implementing
           a DHT for use as storage in a GNS implementation.
           DHTs with reasonable security and performance properties exist
           <xref target="R5N"/>.
           It should also be taken into consideration that GNS implementations
           which build upon different DHT overlays are unlikely to be
           interoperable with each other.
         </t>
       </section>
       <section anchor="security_rev" numbered="true" toc="default">
         <name>Revocations</name>
         <t>
           Zone administrators are advised to pre-generate zone revocations
           and to securely store the revocation information in case the zone
           key is lost, compromised or replaced in the future.
           Pre-calculated revocations can cease to be valid due to expirations
           or protocol changes such as epoch adjustments.
           Consequently, implementers and users must take precautions in order
           to manage revocations accordingly.
         </t>
         <t>
           Revocation payloads do not include a 'new' key for key replacement.
           Inclusion of such a key would have two major disadvantages:
         </t>
         <ol>
           <li>
           If a revocation is published after a private key was compromised,
           allowing key replacement would be dangerous: if an
           adversary took over the private key, the adversary could then
           broadcast a revocation with a key replacement. For the replacement,
           the compromised owner would have no chance to issue even a
           revocation. Thus, allowing a revocation message to replace a private
           key makes dealing with key compromise situations worse.
           </li>
           <li>
           Sometimes, key revocations are used with the objective of changing
           cryptosystems. Migration to another cryptosystem by replacing keys
           via a revocation message would only be secure as long as both
           cryptosystems are still secure against forgery. Such a planned,
           non-emergency migration to another cryptosystem should be done by
           running zones for both cipher systems in parallel for a while. The
           migration would conclude by revoking the legacy zone key only once
           it is deemed no longer secure, and hopefully after most users have
           migrated to the replacement.
           </li>
         </ol>
       </section>
       <section anchor="privacy_labels" numbered="true" toc="default">
         <name>Zone Privacy</name>
         <t>
           GNS does not support authenticated denial of existence of names
           within a zone.
           Record blocks are published in encrypted form using keys derived from the
           zone key and record label. Zone administrators should
           carefully consider if the label and zone key is public or if
           those should be used and considered as a shared secret.
           Unlike zone keys, labels can also be guessed by
           an attacker in the network observing queries and responses. Given
           a known and targeted zone key, the use of well known or easily guessable
           labels effectively results in general disclosure of the records to
           the public.
           If the labels and hence the records should be kept secret except to
           those knowing a secret label and the zone in which to look, the
           label must be chosen accordingly. It is recommended to then use a
           label with sufficient entropy as to prevent guessing attacks.
         </t>
         <t>
           It should be noted that this attack on labels only applies if the
           zone key is somehow disclosed to the adversary. GNS itself
           does not disclose it during a lookup or when resource records are
           published as the zone keys are blinded beforehand.  However,
           zone keys do become public during revocation.
         </t>
       </section>
       <section anchor="namespace_ambiguity">
         <name>Namespace Ambiguity</name>
         <t>
           Some GNS names are indistinguishable from DNS names in their
           respective common display format <xref target="RFC8499"/> or
           other special-use domain names <xref target="RFC6761"/>.
           Given such a name it is ambiguous which name system should be used
           by an application in order to resolve it.
           This poses a risk when trying to resolve a name through DNS when
           it is actually a GNS name.
           In such a case, the GNS name is likely to be leaked as part of the DNS
           resolution.
         </t>
         <t>
           In order to prevent disclosure of queried GNS names it is
           <bcp14>RECOMMENDED</bcp14> that GNS-aware applications try to resolve
           a given name in GNS before any other method taking into account
           potential suffix-to-zone mappings and zTLDs.
           Suffix-to-zone mappings are expected to be configured by the user or
           local administrator and as such the resolution in GNS is
           in line with user expectations even if the name could also be resolved
           through DNS.
           If no suffix-to-zone mapping for the name exists and no zTLD is found,
           resolution <bcp14>MAY</bcp14> continue with other methods such as DNS.
           If a suffix-to-zone mapping for the name exists or the name ends with
           a zTLD, it <bcp14>MUST</bcp14> be resolved using GNS and
           resolution <bcp14>MUST NOT</bcp14> continue by any other means
           independent of the GNS resolution result.
         </t>
         <t>
           Mechanisms such as the Name Service Switch (NSS) of Unix-like
           operating systems are an example of how such a resolution process
           can be implemented and used.
           It allows system administrators to configure host name resolution
           precedence and is integrated with the system resolver implementation.
         </t>
         <t>
           The user or system administrator <bcp14>MAY</bcp14> configure one or
           more unique suffixes for all suffix-to-zone mappings.
           If this suffix is a special-use domain name for GNS or an unreserved
           DNS TLD, this prevents namespace ambiguity through local configuration.
         </t>
       </section>
     </section>
     <section anchor="gana" numbered="true" toc="default">
       <name>GANA Considerations</name>
       <t>
         GANA <xref target="GANA" />
         manages the "GNU Name System Record Types" registry.
         Each entry has the following format:
       </t>
       <ul>
         <li>Name: The name of the record type (case-insensitive ASCII
           string, restricted to alphanumeric characters. For zone delegation
       records, the assigned number represents the ztype value of the zone.</li>
         <li>Number: 32-bit, above 65535</li>
         <li>Comment: Optionally, a brief English text describing the purpose of
           the record type (in UTF-8)</li>
         <li>Contact: Optionally, the contact information of a person to contact for
           further information.</li>
         <li>References: Optionally, references describing the record type
           (such as an RFC)</li>
       </ul>
       <t>
         The registration policy for this registry is "First Come First
         Served". This policy is modeled on that described in <xref target="RFC8126"/>,
         and describes the actions taken by GANA:
       </t>
       <t>
         <!-- FIXME: Unclear who are the experts how are they selected and
         by whom? GNUnet e.V. Politbüro? The DAO?
         Unreserved/Reserved for private use record type range? -->
         Adding new records is possible after expert review, using a
         first-come-first-served policy for unique name allocation.
         Experts are responsible to ensure that the chosen "Name" is
         appropriate for the record type.
         The registry will assign a unique number for the entry.
       </t>
       <t>
         The current contact(s) for expert review are reachable at
         gns-registry@gnunet.org.
       </t>
       <t>
         Any request <bcp14>MUST</bcp14> contain a unique name and a point of contact.
         The contact information <bcp14>MAY</bcp14> be added to the registry given the consent
         of the requester.
         The request <bcp14>MAY</bcp14> optionally also contain relevant references as well
         as a descriptive comment as defined above.
       </t>
       <t>
         GANA has assigned numbers for the record types defined in this
         specification in the "GNU Name System Record Types" registry
         as listed in <xref target="figure_rrtypenums"/>.
       </t>
       <figure anchor="figure_rrtypenums" title="The GANA Resource Record Registry.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
Number | Name    | Contact | References | Comment
-------+---------+---------+------------+-------------------------
65536  | PKEY    | N/A     | [This.I-D] | GNS zone delegation (PKEY)
65537  | NICK    | N/A     | [This.I-D] | GNS zone nickname
65538  | LEHO    | N/A     | [This.I-D] | GNS legacy hostname
65540  | GNS2DNS | N/A     | [This.I-D] | Delegation to DNS
65541  | BOX     | N/A     | [This.I-D] | Boxed records
65551  | REDIRECT| N/A     | [This.I-D] | Redirection record.
65556  | EDKEY   | N/A     | [This.I-D] | GNS zone delegation (EDKEY)
           ]]></artwork>
       </figure>
       <t>
         GANA has assigned signature purposes in its
         "GNUnet Signature Purpose" registry as listed in
         <xref target="figure_purposenums"/>.
       </t>
       <figure anchor="figure_purposenums" title="Requested Changes in the GANA GNUnet Signature Purpose Registry.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
Purpose | Name            | References | Comment
--------+-----------------+------------+--------------------------
  3     | GNS_REVOCATION  | [This.I-D] | GNS zone key revocation
 15     | GNS_RECORD_SIGN | [This.I-D] | GNS record set signature
           ]]></artwork>
       </figure>
     </section>
     <!-- gana -->
     <section>
       <name>IANA Considerations</name>
       <t>
         This document makes no requests for IANA action.
         This section may be removed on publication as an RFC.
       </t>
     </section>
     <section>
       <name>Implementation and Deployment Status</name>
       <t>
         There are two implementations conforming to this specification written
         in C and Go, respectively. The C implementation as part of GNUnet
         <xref target="GNUnetGNS"/> represents the original
         and reference implementation. The Go implementation
         <xref target="GoGNS"/> demonstrates how two implementations of GNS are
         interoperable if they are built on top of the same underlying
         DHT storage.
       </t>
       <t>
         Currently, the GNUnet peer-to-peer network <xref target="GNUnet"/>
         is an active deployment of GNS on top of its <xref target="R5N"/>
         DHT. The <xref target="GoGNS"/> implementation uses this deployment
         by building on top of the GNUnet DHT services available on any
         GNUnet peer. It shows how GNS implementations
         can attach to this existing deployment and participate in name
         resolution as well as zone publication.
       </t>
       <t>
         The self-sovereign identity system re:claimID <xref target="reclaim"/>
         is using GNS in order to selectively share identity attributes and
         attestations with third parties.
       </t>
       <t>
         The Ascension tool <xref target="Ascension"/> facilitates the migration of DNS zones to
         GNS zones by translating information retrieved from a DNS zone
         transfer into a GNS zone.
       </t>
     </section>
     <section>
        <name>Acknowledgements</name>
        <t>
          The authors thank all reviewers for their comments. In particular,
          we thank D. J. Bernstein, S. Bortzmeyer, A. Farrel, E. Lear and R. Salz for their
          insightful and detailed technical reviews. We thank J. Yao and J. Klensin for the
          internationalization reviews. We thank NLnet and NGI DISCOVERY for funding
          work on the GNU Name System.
        </t>
     </section>
   </middle>
   <back>
     <references>
       <name>Normative References</name>

       &RFC1034;
       &RFC1035;
       &RFC2782;
       &RFC2119;
       &RFC3629;
       &RFC3686;
       &RFC3826;
       &RFC5237;
       &RFC5869;
       &RFC5890;
       &RFC5895;
       &RFC6234;
       &RFC6895;
       &RFC6979;
       &RFC7748;
       &RFC8032;
       &RFC8126;
       &RFC8174;
       &RFC8499;
       &RFC9106;

       <reference anchor="GANA" target="https://gana.gnunet.org/">
         <front>
           <title>GNUnet Assigned Numbers Authority (GANA)</title>
           <author><organization>GNUnet e.V.</organization>
           </author>
           <date month="April" year="2020" />
         </front>
       </reference>

       <reference anchor="MODES" target="https://doi.org/10.6028/NIST.SP.800-38A">
         <front>
           <title>Recommendation for Block Cipher Modes of Operation: Methods and Techniques</title>
          <author initials="M." surname="Dworkin" fullname="Morris Dworkin">
            <organization>NIST</organization>
          </author>

           <date year="2001" month="December"/>
           <abstract>
             <t>
               This recommendation defines five confidentiality modes of operation for use with an underlying symmetric key block cipher algorithm: Electronic Codebook (ECB), Cipher Block Chaining (CBC), Cipher Feedback (CFB), Output Feedback (OFB), and Counter (CTR). Used with an underlying block cipher algorithm that is approved in a Federal Information Processing Standard (FIPS), these modes can provide cryptographic protection for sensitive, but unclassified, computer data.
             </t>
           </abstract>
         </front>
       </reference>
       <!--       <reference anchor="GCM" target="https://doi.org/10.6028/NIST.SP.800-38D">
         <front>
           <title>Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC</title>
          <author initials="M." surname="Dworkin" fullname="Morris Dworkin">
            <organization>NIST</organization>
          </author>

           <date year="2007" month="November"/>
           <abstract>
             <t>
               This Recommendation specifies the Galois/Counter Mode (GCM), an algorithm for authenticated encryption with associated data, and its specialization, GMAC, for generating a message authentication code (MAC) on data that is not encrypted. GCM and GMAC are modes of operation for an underlying approved symmetric key block cipher.
             </t>
           </abstract>
         </front>
       </reference>-->
      <reference anchor="CrockfordB32" target="https://www.crockford.com/base32.html">
         <front>
           <title>Base32</title>
          <author initials="D." surname="Douglas" fullname="Crockford">
          </author>

           <date year="2019" month="March"/>
         </front>
       </reference>
       <reference anchor="XSalsa20" target="https://cr.yp.to/snuffle/xsalsa-20110204.pdf">
         <front>
           <title>Extending the Salsa20 nonce</title>
          <author initials="D." surname="Bernstein" fullname="Daniel Bernstein">
            <organization>University of Illinois at Chicago</organization>
          </author>
           <date year="2011"/>
         </front>
       </reference>
       <reference anchor="Unicode-UAX15" target="http://www.unicode.org/reports/tr15/tr15-31.html">
         <front>
           <title>Unicode Standard Annex #15: Unicode Normalization Forms, Revision 31</title>
          <author>
            <organization>The Unicode Consortium</organization>
          </author>
           <date year="2009" month="September"/>
         </front>
       </reference>
       <reference anchor="Unicode-UTS46" target="https://www.unicode.org/reports/tr46">
         <front>
           <title>Unicode Technical Standard #46: Unicode IDNA Compatibility Processing, Revision 27</title>
          <author>
            <organization>The Unicode Consortium</organization>
          </author>
           <date year="2021" month="August"/>
         </front>
       </reference>




             <!--    <reference anchor="ISO20022">
         <front>
         <title>ISO 20022 Financial Services - Universal financial industry message scheme</title>
         <author>
         <organization>International Organization for Standardization</organization>
         <address>
         <uri>http://www.iso.ch</uri>
         </address>
         </author>
         <date month="May" year="2013"/>
         </front>
       </reference>-->
     </references>
     <references>
       <name>Informative References</name>
         &RFC4033;
         &RFC6066;
         &RFC7363;
         &RFC8324;
         &RFC8806;
         &RFC6761;

       <!--         &RFC3912;-->

       <reference anchor="Tor224" target="https://gitweb.torproject.org/torspec.git/tree/proposals/224-rend-spec-ng.txt#n2135">
         <front>
           <title>Next-Generation Hidden Services in Tor</title>
          <author initials="D." surname="Goulet" fullname="David Goulet">
          </author>
          <author initials="G." surname="Kadianakis" fullname="George Kadianakis">
          </author>
          <author initials="N." surname="Mathewson" fullname="Nick Mathewson">
          </author>

           <date year="2013" month="November"/>
         </front>
       </reference>
       <reference anchor="SDSI" target="http://people.csail.mit.edu/rivest/Sdsi10.ps">
         <front>
           <title>SDSI - A Simple Distributed Security Infrastructure</title>
           <author initials="R." surname="Rivest" fullname="Ron Rivest">
           </author>
           <author initials="B." surname="Lampson" fullname="Butler Lampson">
           </author>
           <date year="1996" month="April"/>
        </front>
       </reference>
       <reference anchor="Kademlia" target="http://css.csail.mit.edu/6.824/2014/papers/kademlia.pdf">
         <front>
           <title>Kademlia: A peer-to-peer information system based on the xor metric.</title>
          <author initials="P." surname="Maymounkov" fullname="Petar Maymounkov">
          </author>

          <author initials="D." surname="Mazieres"
            fullname="David Mazieres">
        </author>
           <date year="2002"/>
         </front>
       </reference>
       <!--<reference anchor="Ipfs" target="https://arxiv.org/pdf/1407.3561">
         <front>
           <title>Ipfs-content addressed, versioned, p2p file system.</title>
          <author initials="J." surname="Benet" fullname="Juan Benet">
          </author>
           <date year="2014"/>
         </front>
       </reference>
       -->

       <reference anchor="ed25519" target="https://ed25519.cr.yp.to/ed25519-20110926.pdf">
         <front>
           <title>High-Speed High-Security Signatures</title>
          <author initials="D." surname="Bernstein" fullname="Daniel Bernstein">
            <organization>University of Illinois at Chicago</organization>
          </author>

          <author initials="N." surname="Duif"
            fullname="Niels Duif">
          <organization>Technische Universiteit Eindhoven</organization>

        </author>
          <author initials="T." surname="Lange"
            fullname="Tanja Lange">
          <organization>Technische Universiteit Eindhoven</organization>

          </author>
          <author initials="P." surname="Schwabe"
            fullname="Peter Schwabe">
          <organization>National Taiwan University</organization>

          </author>
          <author initials="B." surname="Yang"
            fullname="Bo-Yin Yang">
          <organization>Academia Sinica</organization>

          </author>
           <date year="2011"/>
         </front>
       </reference>
       <reference anchor="GNS" target="https://sci-hub.st/10.1007/978-3-319-12280-9_9">
         <front>
           <title>A Censorship-Resistant, Privacy-Enhancing and Fully Decentralized Name System</title>
          <author initials="M." surname="Wachs" fullname="Matthias Wachs">
            <organization>Technische Universität München</organization>
          </author>

          <author initials="M." surname="Schanzenbach" fullname="Martin Schanzenbach">
            <organization>Technische Universität München</organization>
          </author>

          <author initials="C." surname="Grothoff"
            fullname="Christian Grothoff">
          <organization>Technische Universität München</organization>
          </author>
           <date year="2014"/>
         </front>
       </reference>
      <reference anchor="R5N" target="https://sci-hub.st/10.1109/ICNSS.2011.6060022">
         <front>
           <title>R5N: Randomized recursive routing for restricted-route networks</title>
          <author initials="N. S." surname="Evans" fullname="Nathan S. Evans">
            <organization>Technische Universität München</organization>
          </author>

          <author initials="C." surname="Grothoff"
            fullname="Christian Grothoff">
          <organization>Technische Universität München</organization>
          </author>
           <date year="2011"/>
         </front>
       </reference>
       <reference anchor="SecureNS" target="https://sci-hub.st/https://doi.org/10.1016/j.cose.2018.01.018">
         <front>
           <title>Towards secure name resolution on the Internet</title>
          <author initials="C." surname="Grothoff"
            fullname="Christian Grothoff">
          <organization>Bern University of Applied Sciences</organization>
          </author>
          <author initials="M." surname="Wachs"
            fullname="Matthias Wachs">
          <organization>Technische Universität München</organization>
          </author>
          <author initials="M." surname="Ermert"
            fullname="Monika Ermert">
          </author>

          <author initials="J." surname="Appelbaum"
            fullname="Jacob Appelbaum">
          <organization>TU Eindhoven</organization>
          </author>
           <date year="2018"/>
         </front>
       </reference>

       <reference anchor="GNUnetGNS" target="https://git.gnunet.org/gnunet.git/tree/src/gns">
         <front>
           <title>The GNUnet GNS Implementation</title>
          <author>
            <organization>GNUnet e.V.</organization>
          </author>
        </front>
       </reference>
       <reference anchor="Ascension" target="https://git.gnunet.org/ascension.git">
         <front>
           <title>The Ascension Implementation</title>
          <author>
            <organization>GNUnet e.V.</organization>
          </author>
        </front>
       </reference>

       <reference anchor="GNUnet" target="https://gnunet.org">
         <front>
           <title>The GNUnet Project</title>
          <author>
            <organization>GNUnet e.V.</organization>
          </author>
        </front>
      </reference>
       <reference anchor="reclaim" target="https://reclaim.gnunet.org">
         <front>
           <title>The GNUnet Project</title>
          <author>
            <organization>GNUnet e.V.</organization>
          </author>
        </front>
       </reference>

       <reference anchor="GoGNS" target="https://github.com/bfix/gnunet-go/tree/master/src/gnunet/service/gns">
         <front>
           <title>The Go GNS Implementation</title>
          <author initials="B." surname="Fix" fullname="Bernd Fix">
          </author>
        </front>
       </reference>





     </references>
     <section>
       <name>Base32GNS</name>
       <t>
         This table defines the encode symbol and decode symbol for a given
         symbol value.
         It can be used to implement the encoding by reading it as:
         A character "A" or "a" is decoded to a 5 bit value 10 when decoding.
         A 5 bit block with a value of 18 is encoded to the character "J" when encoding.
         If the bit length of the byte string to encode is not a multiple of 5
         it is padded to the next multiple with zeroes.
         In order to further increase tolerance for failures in character
         recognition, the letter "U" <bcp14>MUST</bcp14> be decoded to the same value as the
         letter "V" in Base32GNS.
       </t>
       <figure anchor="CrockfordB32Encode" title="The Base32GNS Alphabet Including the Additional U Encode Symbol.">
         <artwork name="" type="" align="left" alt=""><![CDATA[
Symbol      Decode            Encode
Value       Symbol            Symbol
0           0 O o             0
1           1 I i L l         1
2           2                 2
3           3                 3
4           4                 4
5           5                 5
6           6                 6
7           7                 7
8           8                 8
9           9                 9
10          A a               A
11          B b               B
12          C c               C
13          D d               D
14          E e               E
15          F f               F
16          G g               G
17          H h               H
18          J j               J
19          K k               K
20          M m               M
21          N n               N
22          P p               P
23          Q q               Q
24          R r               R
25          S s               S
26          T t               T
27          V v U u           V
28          W w               W
29          X x               X
30          Y y               Y
31          Z z               Z
         ]]></artwork>
       </figure>
     </section>
     <section>
       <name>Use Cases</name>
       <t>
         This section outlines a number of specific use cases which may
         help to fill the gaps not addressed in the technical specification
         itself.
       </t>
       <section anchor="day_in_zoneowner">
         <name>Zone Dissemination</name>
         <t>
           In order to become a zone owner, it is sufficient to generate
           a zone key and a corresponding secret key using a GNS implementation.
           At this point, the zone owner can manage GNS resource records in a
           local zone database.
           The resource records can then be published by a GNS implementation
           as defined in <xref target="publish"/>.
           For other users to resolve the resource records, respective
           zone information must be disseminated first.
           The zone owner may decide to make the zone key and labels known
           to a selected set of users only or to make this information available
           to the general public.
         </t>
         <t>
           Sharing zone information directly with specific users not only allows
           to potentially preserve zone and record privacy, but also allows
           the zone owner and the user to establish strong trust relationships.
           For example, a bank may send a customer letter with a QR code which
           contains the GNS zone of the bank.
           This allows the user to scan the QR code and establish a strong
           link to the zone of the bank and with it, for example, the IP address
           of the online banking web site.
         </t>
         <t>
           Most Internet services likely want to make their zones available
           to the general public as efficiently as possible.
           First, it is reasonable to assume that zones which are commanding
           high levels of reputation and trust are likely included in the
           default suffix-to-zone mappings of implementations.
           Hence dissemination of a zone through delegation under such zones
           can be a viable path in order to disseminate a zone publicly.
           For example, it is conceivable that organizations such as ICANN
           or country-code top-level domain registrars also manage GNS zones
           and offer registration or delegation services.
         </t>
         <t>
           Following best practices in particularly those relating to
           security and abuse mitigation are methods which allow zone owners
           and aspiring registrars to gain a good reputation and eventually
           trust.
           This includes, of course, diligent protection of private zone key
           material.
           Formalizing such best practices is out of scope of this
           specification and should be addressed in a separate document and take
           <xref target="security"/> into account.
         </t>
       </section>
       <section>
         <name>Suffix-to-zone Configuration</name>
         <t>
           A user is expected to install a GNS implementation if it is not already
           provided through other means such as the operating system
           or the browser.
           It is likely that the implementation ships with a configurable
           default suffix-to-name mapping.
           This means that the user is able to resolve GNS names ending on a
           zTLD or ending on a configured suffix-to-name mapping.
           At this point the user may delete or otherwise modify the
           implementation's default suffix-to-name mapping:
          </t>
          <t>
            Deletion of mappings may become necessary of the
            zone owner referenced by the mapping has lost the trust of the user.
            For example, this could be due to lax registration policies resulting
            in phishing activities.
            Modification and addition of new mappings are means to heal the
            namespace perforation which would occur in the case of a deletion
            or to simply establish a strong direct trust relationship.
            However, this requires the user's knowledge of the respective zone
            keys.
            This information must be retrieved out of band, as illustrated in
            <xref target="day_in_zoneowner"/>:
            A bank may send the user a letter with a QR code which contains the
            GNS zone of the bank.
            Other examples include scanning the QR off the device of a friend,
            from a storefront, or an advertisement.
            The level of trust in the respective zone is contextual and likely
            varies from user to user.
            Trust in a zone provided through a letter from a bank which
            may also include a credit card is certainly different from a zone
            found on a random advertisement in the streets.
            However, this trust is immediately tangible to the user and can
            be reflected in the local naming as well.
          </t>
          <t>
            User clients should facilitate the suffix-to-name modification
            process, for example by providing a QR code reader or other import
            mechanisms.
            Implementations are ideally implemented
            according to best practices and addressing applicable points
            from <xref target="security"/>.
            Formalizing such best practices is out of scope of this
            specification.
         </t>
       </section>
       <section>
         <name>Virtual Hosting</name>
         <t>
           HTTP virtual hosting and TLS Server Name Indication are common
           use cases on the Web.
           The HTTP client such as a browser supplies a DNS name in the HTTP
           "Host"-header or the TLS handshake, respectively.
           This allows the HTTP server to serve the indicated virtual host
           with a matching TLS handshake.
           The unambiguity of DNS names are a prerequisite of those use cases.
         </t>
         <t>
           GNS names are not globally unique.
           But, any resource record in GNS can unambiguously be represented as a
           concatenation of of a GNS label and the zTLD of the zone.
           While not human-readable, this property of GNS names can be
           leveraged in order to facilitate the same use cases.
         </t>
         <t>
            Consider the GNS name "www.example.gns" entered in a GNS-aware
            HTTP client.
            At first, "www.example.gns" is resolved using GNS yielding a record
            set.
            Then, the HTTP client determines the virtual host as follows:
          </t>
          <t>
            If there is a LEHO record (<xref target="gnsrecords_leho"/>) in
            the record set, then the HTTP client uses the record value in the
            "Host"-header field of the HTTP request:
          </t>
          <artwork name="" type="" align="left" alt=""><![CDATA[
GET / HTTP/1.1
Host: www.example.com
          ]]></artwork>
           <t>
              If there is no LEHO record in the record set,
              then the HTTP client tries to find the zone of the record
              and translates the GNS name into an unabiguous
              zTLD-representation before using it in the "Host"-header field of
             the HTTP request:
           </t>
           <artwork name="" type="" align="left" alt=""><![CDATA[
GET / HTTP/1.1
Host: www.000G0037FH3QTBCK15Y8BCCNRVWPV17ZC7TSGB1C9ZG2TPGHZVFV1GMG3W
           ]]></artwork>
          <t>
            In order to determine a canonical representation of the record with
            a zTLD, at most two queries are required:
            First, it must be checked whether "www.example.com" itself points to
            a zone delegation record which would imply that the record set which
            was originally resolved is published under the apex label.
            If it does, the unique GNS name is simply the zTLD representation
            of the delegated zone:
          </t>
          <artwork name="" type="" align="left" alt=""><![CDATA[
GET / HTTP/1.1
Host: 000G0037FH3QTBCK15Y8BCCNRVWPV17ZC7TSGB1C9ZG2TPGHZVFV1GMG3W
            ]]></artwork>
          <t>
            If it does not, the unique GNS name is the concatenation of the
            label "www" and the zTLD representation of the zone as given in the
            example above.
            In any case, this representation is globally unique.
            As such, it can be configured by the HTTP server administrator as a
            virtual host name.
          </t>
          <t>
            If the HTTP client is a browser, the use of a unique GNS name
            for virtual hosting or TLS SNI does not necessarily have to be
            shown to the user.
            For example, the name in the URL bar may remain as "www.example.gnu"
            even if the used unique name differs.
          </t>
       </section>
     </section>
     <section>
       <name>Example flows</name>
       <section>
         <name>AAAA Example Resolution</name>
         <figure anchor="figure_resolution_ex_aaaa" title="Example resolution of an IPv6 address.">
           <artwork name="" type="" align="left" alt=""><![CDATA[
                           Local Host             |   Remote
                                                  |   Storage
                                                  |
                                                  |    +---------+
                                                  |   /         /|
                                                  |  +---------+ |
+-----------+ (1)      +----------+               |  |         | |
|           |          |          |      (4,6)    |  | Record  | |
|Application|----------| Resolver |---------------|->| Storage | |
|           |<---------|          |<--------------|--|         |/
+-----------+ (8)      +----------+      (5,7)    |  +---------+
                          A                       |
                          |                       |
                    (2,3) |                       |
                          |                       |
                          |                       |
                       +---------+                |
                      /   v     /|                |
                     +---------+ |                |
                     |         | |                |
                     |  Start  | |                |
                     |  Zones  | |                |
                     |         |/                 |
                     +---------+                  |
         ]]></artwork>
         </figure>
         <ol>
           <li>Lookup AAAA record for name: www.example.gns.</li>
           <li>Determine start zone for www.example.gns.</li>
           <li>Start zone: zk0 - Remainder: www.example.</li>
           <li>Calculate q0=SHA512(ZKDF(zk0, "example")) and initiate GET(q0).</li>
           <li>Retrieve and decrypt RRBLOCK consisting of a single PKEY record containing zk1.</li>
           <li>Calculate q1=SHA512(ZKDF(zk1, "www")) and initiate GET(q1).</li>
           <li>Retrieve RRBLOCK consisting of a single AAAA record containing the IPv6 address 2001:db8::1.</li>
           <li>Return record set to application</li>
         </ol>
       </section>
       <section>
         <name>REDIRECT Example Resolution</name>
         <figure anchor="figure_resolution_ex_redir" title="Example resolution of an IPv6 address with redirect.">
           <artwork name="" type="" align="left" alt=""><![CDATA[
                           Local Host              |   Remote
                                                   |   Storage
                                                   |
                                                   |    +---------+
                                                   |   /         /|
                                                   |  +---------+ |
+-----------+ (1)      +----------+                |  |         | |
|           |          |          |      (4,6,8)   |  | Record  | |
|Application|----------| Resolver |----------------|->| Storage | |
|           |<---------|          |<---------------|--|         |/
+-----------+ (10)     +----------+      (5,7,9)   |  +---------+
                          A                        |
                          |                        |
                    (2,3) |                        |
                          |                        |
                          |                        |
                       +---------+                 |
                      /   v     /|                 |
                     +---------+ |                 |
                     |         | |                 |
                     |  Start  | |                 |
                     |  Zones  | |                 |
                     |         |/                  |
                     +---------+                   |
         ]]></artwork>
         </figure>
         <ol>
           <li>Lookup AAAA record for name: www.example.tld.</li>
           <li>Determine start zone for www.example.tld.</li>
           <li>Start zone: zk0 - Remainder: www.example.</li>
           <li>Calculate q0=SHA512(ZKDF(zk0, "example")) and initiate GET(q0).</li>
           <li>Retrieve and decrypt RRBLOCK consisting of a single REDIRECT record containing zk1.</li>
           <li>Calculate q1=SHA512(ZKDF(zk1, "www")) and initiate GET(q1).</li>
           <li>Retrieve and decrypt RRBLOCK consisting of a single REDIRECT record containing www2.+.</li>
           <li>Calculate q2=SHA512(ZKDF(zk1, "www2")) and initiate GET(q2).</li>
           <li>Retrieve and decrypt RRBLOCK consisting of a single AAAA record containing the IPv6 address 2001:db8::1.</li>
           <li>Return record set to application.</li>
         </ol>
       </section>
       <section>
         <name>GNS2DNS Example Resolution</name>
         <figure anchor="figure_resolution_ex_gnsdns" title="Example resolution of an IPv6 address with DNS handover.">
           <artwork name="" type="" align="left" alt=""><![CDATA[
                           Local Host                |   Remote
                                                     |   Storage
                                                     |
                                                     |    +---------+
                                                     |   /         /|
                                                     |  +---------+ |
+-----------+ (1)      +----------+                  |  |         | |
|           |          |          |      (4)         |  | Record  | |
|Application|----------| Resolver |------------------|->| Storage | |
|           |<---------|          |<-----------------|--|         |/
+-----------+ (8)      +----------+      (5)         |  +---------+
                          A    A                     |
                          |    |    (6,7)            |
                    (2,3) |    +----------+          |
                          |               |          |
                          |               v          |
                       +---------+    +------------+ |
                      /   v     /|    | System DNS | |
                     +---------+ |    | resolver   | |
                     |         | |    +------------+ |
                     |  Start  | |                   |
                     |  Zones  | |                   |
                     |         |/                    |
                     +---------+                     |
         ]]></artwork>
         </figure>
         <ol>
           <li>Lookup AAAA record for name: www.example.gnu</li>
           <li>Determine start zone for www.example.gnu.</li>
           <li>Start zone: zk0 - Remainder: www.example.</li>
           <li>Calculate q0=SHA512(ZKDF(zk0, "example")) and initiate GET(q0).</li>
           <li>Retrieve and decrypt RRBLOCK consisting of a single GNS2DNS record containing the name example.com and the DNS server IPv4 address 192.0.2.1.</li>
           <li>Use system resolver to lookup an AAAA record for the DNS name www.example.com.</li>
           <li>Retrieve a DNS reply consisting of a single AAAA record containing the IPv6 address 2001:db8::1.</li>
           <li>Return record set to application.</li>
         </ol>
       </section>

     </section>
     <section>
       <name>Test Vectors</name>
       <t>
         The following are test vectors for the Base32GNS encoding used for zTLDs.
         The strings are encoded without the zero terminator.
       </t>
       <artwork name="" type="" align="left" alt="">
         <![CDATA[
Base32GNS-Encode:
  Input string: "Hello World"
  Output string: "91JPRV3F41BPYWKCCG"

  Input bytes: 474e55204e616d652053797374656d
  Output string: "8X75A82EC5PPA82KF5SQ8SBD"

Base32GNS-Decode:
  Input string: "91JPRV3F41BPYWKCCG"
  Output string: "Hello World"

  Input string: "91JPRU3F41BPYWKCCG"
  Output string: "Hello World"
           ]]>
       </artwork>
       <t>
         The following test vectors can be used by implementations to test
         for conformance with this specification.
         The test vectors include record sets with a variety
         of record types and flags for both PKEY and EDKEY zones.
         Unless indicated otherwise, the test vectors are provided as
         hex byte values.
         This includes labels as some test vectors contain UTF-8 multibyte
         characters to demonstrate internationalized labels.
       </t>
       <artwork name="" type="" align="left" alt="">
         <![CDATA[
Zone private key (d, big-endian):
50d7b652a4efeadf
f37396909785e595
2171a02178c8e7d4
50fa907925fafd98

Zone identifier (ztype|zkey):
00010000677c477d
2d93097c85b195c6
f96d84ff61f5982c
2c4fe02d5a11fedf
b0c2901f

zTLD:
000G0037FH3QTBCK15Y8BCCNRVWPV17ZC7TSGB1C9ZG2TPGHZVFV1GMG3W

Label:
7465737464656c65
676174696f6e

Number of records (integer): 1

Record #0 := (
EXPIRATION:
0008c06fb9281580

DATA_SIZE:
0020

TYPE:
00010000

FLAGS: 0001

DATA:
21e3b30ff93bc6d3
5ac8c6e0e13afdff
794cb7b44bbbc748
d259d0a0284dbe84

)

RDATA:
0008c06fb9281580
0020000100010000
21e3b30ff93bc6d3
5ac8c6e0e13afdff
794cb7b44bbbc748
d259d0a0284dbe84

Encryption NONCE|EXPIRATION|BLOCK COUNTER:
e90a00610008c06f
b928158000000001

Encryption key (K):
864e7138eae7fd91
a30136899c132b23
acebdb2cef43cb19
f6bf55b67db9b3b3

Storage key (q):
4adc67c5ecee9f76
986abd71c2224a3d
ce2e917026c9a09d
fd44cef3d20f55a2
7332725a6c8afbbb
b0f7ec9af1cc4264
1299406b04fd9b5b
5791f86c4b08d5f4

BDATA:
41dc7b5f2176ba59
1998afb9e3c82579
5050afc4b53d68e4
1ed921da89de51e7
da35a295b59c2b8a
aea4399148d50cff

RRBLOCK:
000000a000010000
182bb636eda79f79
5711bc2708adbb24
2a60446ad3c30803
121d03d348b7ceb6
01beab944aff7ccc
51bffb212779c341
87660c625d1ceb59
d5a0a9a2dfe4072d
0f08cd2ab1e9ed63
d3898ff732521b57
317a6c4950e1984d
74df015f9eb72c4a
0008c06fb9281580
41dc7b5f2176ba59
1998afb9e3c82579
5050afc4b53d68e4
1ed921da89de51e7
da35a295b59c2b8a
aea4399148d50cff

Zone private key (d, big-endian):
50d7b652a4efeadf
f37396909785e595
2171a02178c8e7d4
50fa907925fafd98

Zone identifier (ztype|zkey):
00010000677c477d
2d93097c85b195c6
f96d84ff61f5982c
2c4fe02d5a11fedf
b0c2901f

zTLD:
000G0037FH3QTBCK15Y8BCCNRVWPV17ZC7TSGB1C9ZG2TPGHZVFV1GMG3W

Label:
e5a4a9e4b88be784
a1e695b5

Number of records (integer): 3

Record #0 := (
EXPIRATION:
0008c06fb9281580

DATA_SIZE:
0010

TYPE:
0000001c

FLAGS: 0000

DATA:
0000000000000000
00000000deadbeef

)

Record #1 := (
EXPIRATION:
00b00f81b7449b40

DATA_SIZE:
0006

TYPE:
00010001

FLAGS: 8000

DATA:
e6849be7a7b0

)

Record #2 := (
EXPIRATION:
000000016b597108

DATA_SIZE:
000b

TYPE:
00000010

FLAGS: 4004

DATA:
48656c6c6f20576f
726c64

)

RDATA:
0008c06fb9281580
001000000000001c
0000000000000000
00000000deadbeef
00b00f81b7449b40
0006800000010001
e6849be7a7b00000
00016b597108000b
4004000000104865
6c6c6f20576f726c
6400000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000

Encryption NONCE|EXPIRATION|BLOCK COUNTER:
ee9633c10005db3b
cdbd617c00000001

Encryption key (K):
fb3ab5de23bddae1
997aaf7b92c2d271
51408b77af7a41ac
79057c4df5383d01

Storage key (q):
aff0ad6a44097368
429ac476dfa1f34b
ee4c36e7476d07aa
6463ff20915b1005
c0991def91fc3e10
909f8702c0be4043
6778c711f2ca47d5
5cf0b54d235da977

BDATA:
f8c5e4badf1649d4
04da64df7d9d285f
4072a5f7a2547d56
74227e9b188eb2bb
6b34532f61e08ffb
d5bdea3741e60967
b687f8d8c44c8f6f
120a0f980f393b21
60407be128a74a51
51d6370be56a86ea
e32fdc217596b13f
6fea3fcfea0f4deb
881a25458f505a8f
cfca62d6da56073f
497698613475a1ad
14b7877f9455b0ec

RRBLOCK:
000000f000010000
a51296df757ee275
ca118d4f07fa7aae
5508bcf512aa4112
1429d4a0de9d057e
05c095040b10c7f8
187aa5da12287d1c
2910ff04d6f50af1
fa95382e9f007f75
098f620d1ff7c971
28f40d7458a2d3c7
f048ca3820064bdd
ee9413e9548ec994
0005db3bcdbd617c
f8c5e4badf1649d4
04da64df7d9d285f
4072a5f7a2547d56
74227e9b188eb2bb
6b34532f61e08ffb
d5bdea3741e60967
b687f8d8c44c8f6f
120a0f980f393b21
60407be128a74a51
51d6370be56a86ea
e32fdc217596b13f
6fea3fcfea0f4deb
881a25458f505a8f
cfca62d6da56073f
497698613475a1ad
14b7877f9455b0ec

Zone private key (d):
5af7020ee1916032
8832352bbc6a68a8
d71a7cbe1b929969
a7c66d415a0d8f65

Zone identifier (ztype|zkey):
000100143cf4b924
032022f0dc505814
53b85d93b047b63d
446c5845cb48445d
db96688f

zTLD:
000G051WYJWJ80S04BRDRM2R2H9VGQCKP13VCFA4DHC4BJT88HEXQ5K8HW

Label:
7465737464656c65
676174696f6e

Number of records (integer): 1

Record #0 := (
EXPIRATION:
0008c06fb9281580

DATA_SIZE:
0020

TYPE:
00010000

FLAGS: 0001

DATA:
21e3b30ff93bc6d3
5ac8c6e0e13afdff
794cb7b44bbbc748
d259d0a0284dbe84

)

RDATA:
0008c06fb9281580
0020000100010000
21e3b30ff93bc6d3
5ac8c6e0e13afdff
794cb7b44bbbc748
d259d0a0284dbe84

Encryption NONCE|EXPIRATION:
98132ea86859d35c
88bfd317fa991bcb
0008c06fb9281580

Encryption key (K):
85c429a9567aa633
411a9691e9094c45
281672be586034aa
e4a2a2cc716159e2

Storage key (q):
abaabac0e1249459
75988395aac0241e
5559c41c4074e255
7b9fe6d154b614fb
cdd47fc7f51d786d
c2e0b1ece76037c0
a1578c384ec61d44
5636a94e880329e9

BDATA:
9cc455a129331943
5993cb3d67179ec0
6ea8d8894e904a0c
35e91c5c2ff2ed93
9cc2f8301231f44e
592a4ac87e4998b9
4625c64af51686a2
b36a2b2892d44f2d

RRBLOCK:
000000b000010014
9bf233198c6d53bb
dbac495cabd91049
a684af3f4051baca
b0dcf21c8cf27a1a
44d240d07902f490
b7c43ef00758abce
8851c18c70ac6df9
7a88f79211cf875f
784885ca3e349ec4
ca892b9ff084c535
8965b8e74a231595
2d4c8c06521c2f0c
0008c06fb9281580
9cc455a129331943
5993cb3d67179ec0
6ea8d8894e904a0c
35e91c5c2ff2ed93
9cc2f8301231f44e
592a4ac87e4998b9
4625c64af51686a2
b36a2b2892d44f2d

Zone private key (d):
5af7020ee1916032
8832352bbc6a68a8
d71a7cbe1b929969
a7c66d415a0d8f65

Zone identifier (ztype|zkey):
000100143cf4b924
032022f0dc505814
53b85d93b047b63d
446c5845cb48445d
db96688f

zTLD:
000G051WYJWJ80S04BRDRM2R2H9VGQCKP13VCFA4DHC4BJT88HEXQ5K8HW

Label:
e5a4a9e4b88be784
a1e695b5

Number of records (integer): 3

Record #0 := (
EXPIRATION:
0008c06fb9281580

DATA_SIZE:
0010

TYPE:
0000001c

FLAGS: 0000

DATA:
0000000000000000
00000000deadbeef

)

Record #1 := (
EXPIRATION:
00b00f81b7449b40

DATA_SIZE:
0006

TYPE:
00010001

FLAGS: 8000

DATA:
e6849be7a7b0

)

Record #2 := (
EXPIRATION:
000000016b597108

DATA_SIZE:
000b

TYPE:
00000010

FLAGS: 4004

DATA:
48656c6c6f20576f
726c64

)

RDATA:
0008c06fb9281580
001000000000001c
0000000000000000
00000000deadbeef
00b00f81b7449b40
0006800000010001
e6849be7a7b00000
00016b597108000b
4004000000104865
6c6c6f20576f726c
6400000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000
0000000000000000

Encryption NONCE|EXPIRATION:
bb0d3f0fbd224277
50da5d691216e6c9
0005db3bcdbd7769

Encryption key (K):
3df805bd6687aa14
209628c244b11191
88c3925637a41e5d
76496c2945dc377b

Storage key (q):
baf82177eec081e0
74a7da47ffc64877
58fb0df01a6c7fbb
52fc8a31bef029af
74aa0dc15ab8e2fa
7a54b4f5f637f615
8fa7f03c3fcebe78
d3f9d640aac0d1ed

BDATA:
6f79a9fd28bc5e38
2fc931ed22931797
326fdd698129fc47
8a639e902b411088
0a45037c667ff769
5f09c4a7f4f3471a
b2365bf3af79e953
697f1e35f93bd1ad
876971ce70527a3b
82c098d23fffd4a4
0057b694bec43416
4fb83c12b1f4570f
69a28f3bc3b7d838
b2619f6b8e1723ba
78c4b7ce19ef3f39
0405b63f7ce00216
1bdd7f5e9b3622bc
1af2d4ca84fd5fc5

RRBLOCK:
0000010000010014
74f90068f1676953
52a8a6c2eb984898
c53acca0980470c6
c81264cbdd78ad11
13b6b78358a88de7
3c5d22f73f1ad588
ee6f07d13410a2f5
15a074872608ec02
ef9020fdeb4266bf
1177c7e57e786059
97032a3f71f7216c
894e073ac77f2a0d
0005db3bcdbd7769
6f79a9fd28bc5e38
2fc931ed22931797
326fdd698129fc47
8a639e902b411088
0a45037c667ff769
5f09c4a7f4f3471a
b2365bf3af79e953
697f1e35f93bd1ad
876971ce70527a3b
82c098d23fffd4a4
0057b694bec43416
4fb83c12b1f4570f
69a28f3bc3b7d838
b2619f6b8e1723ba
78c4b7ce19ef3f39
0405b63f7ce00216
1bdd7f5e9b3622bc
1af2d4ca84fd5fc5
         ]]>
       </artwork>
       <t>
         The following is an example revocation for a zone:
       </t>
       <artwork name="" type="" align="left" alt="">
         <![CDATA[
Zone private key (d, big-endian scalar):
6fea32c05af58bfa
979553d188605fd5
7d8bf9cc263b78d5
f7478c07b998ed70

Zone identifier (ztype|zkey):
000100002ca223e8
79ecc4bbdeb5da17
319281d63b2e3b69
55f1c3775c804a98
d5f8ddaa

Encoded zone identifier (zTLD):
000G001CM8HYGYFCRJXXXDET2WRS50EP7CQ3PTANY71QEQ409ACDBY6XN8

Difficulty (5 base difficulty + 2 epochs): 7

Signed message:
0000003400000003
0005d66da3598127
000100002ca223e8
79ecc4bbdeb5da17
319281d63b2e3b69
55f1c3775c804a98
d5f8ddaa

Proof:
0005d66da3598127
0000395d1827c000
3ab877d07570f2b8
3ab877d07570f332
3ab877d07570f4f5
3ab877d07570f50f
3ab877d07570f537
3ab877d07570f599
3ab877d07570f5cd
3ab877d07570f5d9
3ab877d07570f66a
3ab877d07570f69b
3ab877d07570f72f
3ab877d07570f7c3
3ab877d07570f843
3ab877d07570f8d8
3ab877d07570f91b
3ab877d07570f93a
3ab877d07570f944
3ab877d07570f98a
3ab877d07570f9a7
3ab877d07570f9b0
3ab877d07570f9df
3ab877d07570fa05
3ab877d07570fa3e
3ab877d07570fa63
3ab877d07570fa84
3ab877d07570fa8f
3ab877d07570fa91
3ab877d07570fad6
3ab877d07570fb0a
3ab877d07570fc0f
3ab877d07570fc43
3ab877d07570fca5
000100002ca223e8
79ecc4bbdeb5da17
319281d63b2e3b69
55f1c3775c804a98
d5f8ddaa053b0259
700039187d1da461
3531502bc4a4eecc
c69900d24f8aac54
30f28fc509270133
1f178e290fe06e82
ce2498ce7b23a340
58e3d6a2f247e92b
c9d7b9ab
         ]]>
       </artwork>
     </section>



     <!-- Change Log
       v00 2017-07-23  MS   Initial version
     -->
   </back>
 </rfc>