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/*
This file is part of GNUnet
(C) 2013 Christian Grothoff (and other contributing authors)
GNUnet is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation; either version 3, or (at your
option) any later version.
GNUnet is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNUnet; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
/**
* @file include/gnunet_secretsharing_service.h
* @brief verified additive secret sharing and cooperative decryption
* @author Florian Dold
*/
#ifndef GNUNET_CONSENSUS_SERVICE_H
#define GNUNET_CONSENSUS_SERVICE_H
#ifdef __cplusplus
extern "C"
{
#if 0 /* keep Emacsens' auto-indent happy */
}
#endif
#endif
#include "platform.h"
#include "gnunet_common.h"
#include "gnunet_time_lib.h"
#include "gnunet_configuration_lib.h"
#include <gcrypt.h>
/**
* Session that will eventually establish a shared secred between
* the involved peers and allow encryption and cooperative decryption.
*/
struct GNUNET_SECRETSHARING_Session;
/**
* Handle to cancel a cooperative decryption operation.
*/
struct GNUNET_SECRETSHARING_DecryptionHandle;
/**
* Parameters of the crypto system.
*/
struct GNUNET_SECRETSHARING_Parameters
{
/**
* Threshold, that is, minimum number of peers that
* must cooperate to decrypt a value.
*/
unsigned int k;
/**
* Prime with p = 2q+1.
*/
gcry_mpi_t p;
/**
* Prime.
*/
gcry_mpi_t q;
/**
* Generator of G_q.
*/
gcry_mpi_t g;
};
/**
* Encrypted field element.
*/
struct GNUNET_SECRETSHARING_Ciphertext
{
/**
* First component.
*/
gcry_mpi_t c1;
/**
* Second component.
*/
gcry_mpi_t c2;
};
/**
* Called once the secret has been established.
*
* @param cls closure
* @param public_key public key of the session
* @param num_ready_peers number of peers in @ready_peers
* @parem ready_peers peers that successfuly participated in establishing
* the shared secret
*/
typedef void (*GNUNET_SECRETSHARING_SecretReadyCallback) (void *cls,
gcry_mpi_t public_key,
unsigned int num_ready_peers,
const struct GNUNET_PeerIdentity *ready_peers);
/**
* Create a session that will eventually establish a shared secret
* with the other peers.
*
* @param cfg configuration to use
* @param num_peers number of peers in @peers
* @param session_id unique session id
* @param deadline point in time where the session must be established; taken as hint
* by underlying consensus sessions
* @param cb called when the secret has been established
* @param cls closure for cb
*/
struct GNUNET_SECRETSHARING_Session *
GNUNET_SECRETSHARING_create_session (const struct GNUNET_CONFIGURATION_Handle *cfg,
unsigned int num_peers,
const struct GNUNET_PeerIdentity *peers,
const struct GNUNET_HashCode *session_id,
struct GNUNET_TIME_Absolute deadline,
struct GNUNET_SECRETSHARING_Parameters *parameters,
GNUNET_SECRETSHARING_SecretReadyCallback *cb,
void *cls);
/**
* Destroy a secret sharing session.
*
* @param session session to destroy
*/
void
GNUNET_SECRETSHARING_destroy_session (struct GNUNET_SECRETSHARING_Session *session);
/**
* Encrypt a value. This operation is executed locally, no communication is
* necessary.
*
* This is a helper function, encryption can be done soley with a session's public key
* and the crypto system parameters.
*
* @param session session to take the key for encryption from,
* the session's ready callback must have been already called
* @param message message to encrypt
* @param result_cyphertext pointer to store the resulting ciphertext
* @return GNUNET_YES on succes, GNUNET_SYSERR if the message is invalid (invalid range)
*/
int
GNUNET_SECRETSHARING_encrypt (const struct GNUNET_SECRETSHARING_Session *session,
gcry_mpi_t message,
struct GNUNET_SECRETSHARING_Ciphertext *result_ciphertext);
/**
* Publish the given ciphertext for decryption. Once a sufficient (>=k) number of peers has
* published the same value, it will be decrypted.
*
* When the operation is canceled, the decrypt_cb is not called anymore, but the calling
* peer may already have irrevocably contributed his share for the decryption of the value.
*
* @param session session to use for the decryption
* @param ciphertext ciphertext to publish in order to decrypt it (if enough peers agree)
* @param decrypt_cb callback called once the decryption succeeded
* @param cls closure for decrypt_cb
* @return handle to cancel the operation
*/
struct GNUNET_SECRETSHARING_DecryptionHandle
GNUNET_SECRETSHARING_publish_decrypt (struct GNUNET_SECRETSHARING_Session *session,
struct GNUNET_SECRETSHARING_Ciphertext *ciphertext,
GNUNET_SECRETSHARING_DecryptCallback decrypt_cb,
void *cls);
/**
* Cancel a decryption.
*
* The decrypt_cb is not called anymore, but the calling
* peer may already have irrevocably contributed his share for the decryption of the value.
*/
void
GNUNET_SECRETSHARING_cancel_decrypt (struct GNUNET_SECRETSHARING_DecryptionHandle *decryption_handle);
#if 0 /* keep Emacsens' auto-indent happy */
{
#endif
#ifdef __cplusplus
}
#endif
#endif
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