1 files changed, 1060 insertions, 0 deletions

diff --git a/src/contrib/service/scalarproduct/gnunet-service-scalarproduct-ecc_bob.c b/src/contrib/service/scalarproduct/gnunet-service-scalarproduct-ecc_bob.c
new file mode 100644
index 000000000..1945f1937
--- /dev/null
+++ b/src/contrib/service/scalarproduct/gnunet-service-scalarproduct-ecc_bob.c
@@ -0,0 +1,1060 @@
+/*
+     This file is part of GNUnet.
+     Copyright (C) 2013-2017, 2021 GNUnet e.V.
+
+     GNUnet is free software: you can redistribute it and/or modify it
+     under the terms of the GNU Affero General Public License as published
+     by the Free Software Foundation, either version 3 of the License,
+     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
+     Affero General Public License for more details.
+
+     You should have received a copy of the GNU Affero General Public License
+     along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+     SPDX-License-Identifier: AGPL3.0-or-later
+ */
+/**
+ * @file scalarproduct/gnunet-service-scalarproduct-ecc_bob.c
+ * @brief scalarproduct service implementation
+ * @author Christian M. Fuchs
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include <limits.h>
+#include <gcrypt.h>
+#include "gnunet_util_lib.h"
+#include "gnunet_core_service.h"
+#include "gnunet_cadet_service.h"
+#include "gnunet_applications.h"
+#include "gnunet_protocols.h"
+#include "gnunet_scalarproduct_service.h"
+#include "gnunet_seti_service.h"
+#include "scalarproduct.h"
+#include "gnunet-service-scalarproduct-ecc.h"
+
+#define LOG(kind, ...) GNUNET_log_from (kind, "scalarproduct-bob", __VA_ARGS__)
+
+
+/**
+ * An encrypted element key-value pair.
+ */
+struct MpiElement
+{
+  /**
+   * Key used to identify matching pairs of values to multiply.
+   * Points into an existing data structure, to avoid copying
+   * and doubling memory use.
+   */
+  const struct GNUNET_HashCode *key;
+
+  /**
+   * Value represented (a).
+   */
+  int64_t value;
+};
+
+
+/**
+ * A scalarproduct session which tracks an offer for a
+ * multiplication service by a local client.
+ */
+struct BobServiceSession
+{
+  /**
+   * The client this request is related to.
+   */
+  struct GNUNET_SERVICE_Client *client;
+
+  /**
+   * Client message queue.
+   */
+  struct GNUNET_MQ_Handle *client_mq;
+
+  /**
+   * All non-0-value'd elements transmitted to us.
+   */
+  struct GNUNET_CONTAINER_MultiHashMap *intersected_elements;
+
+  /**
+   * Set of elements for which we will be conducting an intersection.
+   * The resulting elements are then used for computing the scalar product.
+   */
+  struct GNUNET_SETI_Handle *intersection_set;
+
+  /**
+   * Set of elements for which will conduction an intersection.
+   * the resulting elements are then used for computing the scalar product.
+   */
+  struct GNUNET_SETI_OperationHandle *intersection_op;
+
+  /**
+   * Our open port.
+   */
+  struct GNUNET_CADET_Port *port;
+
+  /**
+   * b(Bob)
+   */
+  struct MpiElement *sorted_elements;
+
+  /**
+   * Product of the g_i^{b_i}
+   */
+  struct GNUNET_CRYPTO_EccPoint prod_g_i_b_i;
+
+  /**
+   * Product of the h_i^{b_i}
+   */
+  struct GNUNET_CRYPTO_EccPoint prod_h_i_b_i;
+
+  /**
+   * How many elements will be supplied in total from the client.
+   */
+  uint32_t total;
+
+  /**
+   * Already transferred elements (received) for multipart
+   * messages from client. Always less than @e total.
+   */
+  uint32_t client_received_element_count;
+
+  /**
+   * How many elements actually are used for the scalar product.
+   * Size of the arrays in @e r and @e r_prime.  Also sometimes
+   * used as an index into the arrays during construction.
+   */
+  uint32_t used_element_count;
+
+  /**
+   * Counts the number of values received from Alice by us.
+   * Always less than @e used_element_count.
+   */
+  uint32_t cadet_received_element_count;
+
+  /**
+   * State of this session.   In
+   * #GNUNET_SCALARPRODUCT_STATUS_ACTIVE while operation is
+   * ongoing, afterwards in #GNUNET_SCALARPRODUCT_STATUS_SUCCESS or
+   * #GNUNET_SCALARPRODUCT_STATUS_FAILURE.
+   */
+  enum GNUNET_SCALARPRODUCT_ResponseStatus status;
+
+  /**
+   * Are we already in #destroy_service_session()?
+   */
+  int in_destroy;
+
+  /**
+   * The CADET channel.
+   */
+  struct GNUNET_CADET_Channel *channel;
+
+  /**
+   * Originator's peer identity. (Only for diagnostics.)
+   */
+  struct GNUNET_PeerIdentity peer;
+
+  /**
+   * (hopefully) unique transaction ID
+   */
+  struct GNUNET_HashCode session_id;
+
+  /**
+   * The message queue for this channel.
+   */
+  struct GNUNET_MQ_Handle *cadet_mq;
+};
+
+
+/**
+ * GNUnet configuration handle
+ */
+static const struct GNUNET_CONFIGURATION_Handle *cfg;
+
+/**
+ * Handle to the CADET service.
+ */
+static struct GNUNET_CADET_Handle *my_cadet;
+
+/**
+ * Context for DLOG operations on a curve.
+ */
+static struct GNUNET_CRYPTO_EccDlogContext *edc;
+
+
+/**
+ * Callback used to free the elements in the map.
+ *
+ * @param cls NULL
+ * @param key key of the element
+ * @param value the value to free
+ */
+static int
+free_element_cb (void *cls,
+                 const struct GNUNET_HashCode *key,
+                 void *value)
+{
+  struct GNUNET_SCALARPRODUCT_Element *element = value;
+
+  GNUNET_free (element);
+  return GNUNET_OK;
+}
+
+
+/**
+ * Destroy session state, we are done with it.
+ *
+ * @param s the session to free elements from
+ */
+static void
+destroy_service_session (struct BobServiceSession *s)
+{
+  if (GNUNET_YES == s->in_destroy)
+    return;
+  s->in_destroy = GNUNET_YES;
+  if (NULL != s->client)
+  {
+    struct GNUNET_SERVICE_Client *c = s->client;
+
+    s->client = NULL;
+    GNUNET_SERVICE_client_drop (c);
+  }
+  if (NULL != s->intersected_elements)
+  {
+    GNUNET_CONTAINER_multihashmap_iterate (s->intersected_elements,
+                                           &free_element_cb,
+                                           NULL);
+    GNUNET_CONTAINER_multihashmap_destroy (s->intersected_elements);
+    s->intersected_elements = NULL;
+  }
+  if (NULL != s->intersection_op)
+  {
+    GNUNET_SETI_operation_cancel (s->intersection_op);
+    s->intersection_op = NULL;
+  }
+  if (NULL != s->intersection_set)
+  {
+    GNUNET_SETI_destroy (s->intersection_set);
+    s->intersection_set = NULL;
+  }
+  if (NULL != s->sorted_elements)
+  {
+    GNUNET_free (s->sorted_elements);
+    s->sorted_elements = NULL;
+  }
+  if (NULL != s->port)
+  {
+    GNUNET_CADET_close_port (s->port);
+    s->port = NULL;
+  }
+  if (NULL != s->channel)
+  {
+    GNUNET_CADET_channel_destroy (s->channel);
+    s->channel = NULL;
+  }
+  GNUNET_free (s);
+}
+
+
+/**
+ * Notify the client that the session has succeeded or failed.  This
+ * message gets sent to Bob's client if the operation completed or
+ * Alice disconnected.
+ *
+ * @param session the associated client session to fail or succeed
+ */
+static void
+prepare_client_end_notification (struct BobServiceSession *session)
+{
+  struct ClientResponseMessage *msg;
+  struct GNUNET_MQ_Envelope *e;
+
+  if (NULL == session->client_mq)
+    return; /* no client left to be notified */
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Sending session-end notification with status %d to client for session %s\n",
+              session->status,
+              GNUNET_h2s (&session->session_id));
+  e = GNUNET_MQ_msg (msg,
+                     GNUNET_MESSAGE_TYPE_SCALARPRODUCT_RESULT);
+  msg->range = 0;
+  msg->product_length = htonl (0);
+  msg->status = htonl (session->status);
+  GNUNET_MQ_send (session->client_mq,
+                  e);
+}
+
+
+/**
+ * Function called whenever a channel is destroyed.  Should clean up
+ * any associated state.
+ *
+ * It must NOT call #GNUNET_CADET_channel_destroy() on the channel.
+ *
+ * @param cls the `struct BobServiceSession`
+ * @param channel connection to the other end (henceforth invalid)
+ */
+static void
+cb_channel_destruction (void *cls,
+                        const struct GNUNET_CADET_Channel *channel)
+{
+  struct BobServiceSession *s = cls;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Peer disconnected, terminating session %s with peer %s\n",
+              GNUNET_h2s (&s->session_id),
+              GNUNET_i2s (&s->peer));
+  s->channel = NULL;
+  if (GNUNET_SCALARPRODUCT_STATUS_ACTIVE == s->status)
+  {
+    s->status = GNUNET_SCALARPRODUCT_STATUS_FAILURE;
+    prepare_client_end_notification (s);
+  }
+  destroy_service_session (s);
+}
+
+
+/**
+ * MQ finished giving our last message to CADET, now notify
+ * the client that we are finished.
+ */
+static void
+bob_cadet_done_cb (void *cls)
+{
+  struct BobServiceSession *session = cls;
+
+  session->status = GNUNET_SCALARPRODUCT_STATUS_SUCCESS;
+  prepare_client_end_notification (session);
+}
+
+
+/**
+ * Bob generates the response message to be sent to Alice.
+ *
+ * @param s the associated requesting session with Alice
+ */
+static void
+transmit_bobs_cryptodata_message (struct BobServiceSession *s)
+{
+  struct EccBobCryptodataMessage *msg;
+  struct GNUNET_MQ_Envelope *e;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Sending response to Alice\n");
+  e = GNUNET_MQ_msg (msg,
+                     GNUNET_MESSAGE_TYPE_SCALARPRODUCT_ECC_BOB_CRYPTODATA);
+  msg->contained_element_count = htonl (2);
+  msg->prod_g_i_b_i = s->prod_g_i_b_i;
+  msg->prod_h_i_b_i = s->prod_h_i_b_i;
+  GNUNET_MQ_notify_sent (e,
+                         &bob_cadet_done_cb,
+                         s);
+  GNUNET_MQ_send (s->cadet_mq,
+                  e);
+}
+
+
+/**
+ * Iterator to copy over messages from the hash map
+ * into an array for sorting.
+ *
+ * @param cls the `struct AliceServiceSession *`
+ * @param key the key (unused)
+ * @param value the `struct GNUNET_SCALARPRODUCT_Element *`
+ */
+static int
+copy_element_cb (void *cls,
+                 const struct GNUNET_HashCode *key,
+                 void *value)
+{
+  struct BobServiceSession *s = cls;
+  struct GNUNET_SCALARPRODUCT_Element *e = value;
+
+  s->sorted_elements[s->used_element_count].value = (int64_t) GNUNET_ntohll (
+    e->value);
+  s->sorted_elements[s->used_element_count].key = &e->key;
+  s->used_element_count++;
+  return GNUNET_OK;
+}
+
+
+/**
+ * Compare two `struct MpiValue`s by key for sorting.
+ *
+ * @param a pointer to first `struct MpiValue *`
+ * @param b pointer to first `struct MpiValue *`
+ * @return -1 for a < b, 0 for a=b, 1 for a > b.
+ * TODO: code duplication with Alice!
+ */
+static int
+element_cmp (const void *a,
+             const void *b)
+{
+  const struct MpiElement *ma = a;
+  const struct MpiElement *mb = b;
+
+  return GNUNET_CRYPTO_hash_cmp (ma->key,
+                                 mb->key);
+}
+
+
+/**
+ * Check a multipart-chunk of a request from another service to
+ * calculate a scalarproduct with us.
+ *
+ * @param cls closure (set from #GNUNET_CADET_connect)
+ * @param msg the actual message
+ * @return #GNUNET_OK to keep the connection open,
+ *         #GNUNET_SYSERR to close it (signal serious error)
+ */
+static int
+check_alices_cryptodata_message (void *cls,
+                                 const struct EccAliceCryptodataMessage *msg)
+{
+  struct BobServiceSession *s = cls;
+  uint32_t contained_elements;
+  size_t msg_length;
+  uint16_t msize;
+  unsigned int max;
+
+  msize = ntohs (msg->header.size);
+  if (msize <= sizeof(struct EccAliceCryptodataMessage))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  contained_elements = ntohl (msg->contained_element_count);
+  /* Our intersection may still be ongoing, but this is nevertheless
+     an upper bound on the required array size */
+  max = GNUNET_CONTAINER_multihashmap_size (s->intersected_elements);
+  msg_length = sizeof(struct EccAliceCryptodataMessage)
+               + contained_elements * sizeof(struct GNUNET_CRYPTO_EccPoint) * 2;
+  if ((msize != msg_length) ||
+      (0 == contained_elements) ||
+      (contained_elements > UINT16_MAX) ||
+      (max < contained_elements + s->cadet_received_element_count))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Handle a multipart-chunk of a request from another service to
+ * calculate a scalarproduct with us.
+ *
+ * @param cls closure (set from #GNUNET_CADET_connect)
+ * @param msg the actual message
+ */
+static void
+handle_alices_cryptodata_message (void *cls,
+                                  const struct EccAliceCryptodataMessage *msg)
+{
+  struct BobServiceSession *s = cls;
+  const struct GNUNET_CRYPTO_EccPoint *payload;
+  uint32_t contained_elements;
+  unsigned int max;
+  const struct GNUNET_CRYPTO_EccPoint *g_i;
+  const struct GNUNET_CRYPTO_EccPoint *h_i;
+  struct GNUNET_CRYPTO_EccPoint g_i_b_i;
+  struct GNUNET_CRYPTO_EccPoint h_i_b_i;
+
+  contained_elements = ntohl (msg->contained_element_count);
+  max = GNUNET_CONTAINER_multihashmap_size (s->intersected_elements);
+  /* sort our vector for the computation */
+  if (NULL == s->sorted_elements)
+  {
+    s->sorted_elements
+      = GNUNET_new_array (GNUNET_CONTAINER_multihashmap_size (
+                            s->intersected_elements),
+                          struct MpiElement);
+    s->used_element_count = 0;
+    GNUNET_CONTAINER_multihashmap_iterate (s->intersected_elements,
+                                           &copy_element_cb,
+                                           s);
+    qsort (s->sorted_elements,
+           s->used_element_count,
+           sizeof(struct MpiElement),
+           &element_cmp);
+  }
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Received %u crypto values from Alice\n",
+              (unsigned int) contained_elements);
+  payload = (const struct GNUNET_CRYPTO_EccPoint *) &msg[1];
+
+  for (unsigned int i = 0; i < contained_elements; i++)
+  {
+    int64_t val = s->sorted_elements[i + s->cadet_received_element_count].value;
+    struct GNUNET_CRYPTO_EccScalar vali;
+
+    GNUNET_assert (INT64_MIN != val);
+    GNUNET_CRYPTO_ecc_scalar_from_int (val > 0 ? val : -val,
+                                       &vali);
+    if (val < 0)
+      crypto_core_ed25519_scalar_negate (vali.v,
+                                         vali.v);
+    g_i = &payload[i * 2];
+    /* g_i_b_i = g_i^vali */
+    GNUNET_assert (GNUNET_OK ==
+                   GNUNET_CRYPTO_ecc_pmul_mpi (g_i,
+                                               &vali,
+                                               &g_i_b_i));
+    h_i = &payload[i * 2 + 1];
+    /* h_i_b_i = h_i^vali */
+    GNUNET_assert (GNUNET_OK ==
+                   GNUNET_CRYPTO_ecc_pmul_mpi (h_i,
+                                               &vali,
+                                               &h_i_b_i));
+    if (0 == i + s->cadet_received_element_count)
+    {
+      /* first iteration, nothing to add */
+      s->prod_g_i_b_i = g_i_b_i;
+      s->prod_h_i_b_i = h_i_b_i;
+    }
+    else
+    {
+      /* further iterations, cummulate resulting value */
+      GNUNET_assert (GNUNET_OK ==
+                     GNUNET_CRYPTO_ecc_add (&s->prod_g_i_b_i,
+                                            &g_i_b_i,
+                                            &s->prod_g_i_b_i));
+      GNUNET_assert (GNUNET_OK ==
+                     GNUNET_CRYPTO_ecc_add (&s->prod_h_i_b_i,
+                                            &h_i_b_i,
+                                            &s->prod_h_i_b_i));
+    }
+  }
+  s->cadet_received_element_count += contained_elements;
+  if ((s->cadet_received_element_count == max) &&
+      (NULL == s->intersection_op))
+  {
+    /* intersection has finished also on our side, and
+       we got the full set, so we can proceed with the
+       CADET response(s) */
+    transmit_bobs_cryptodata_message (s);
+  }
+  GNUNET_CADET_receive_done (s->channel);
+}
+
+
+/**
+ * Callback for set operation results. Called for each element
+ * that needs to be removed from the result set.
+ *
+ * @param cls closure with the `struct BobServiceSession`
+ * @param element a result element, only valid if status is #GNUNET_SETI_STATUS_OK
+ * @param current_size current set size
+ * @param status what has happened with the set intersection?
+ */
+static void
+cb_intersection_element_removed (void *cls,
+                                 const struct GNUNET_SETI_Element *element,
+                                 uint64_t current_size,
+                                 enum GNUNET_SETI_Status status)
+{
+  struct BobServiceSession *s = cls;
+  struct GNUNET_SCALARPRODUCT_Element *se;
+
+  switch (status)
+  {
+  case GNUNET_SETI_STATUS_DEL_LOCAL:
+    /* this element has been removed from the set */
+    se = GNUNET_CONTAINER_multihashmap_get (s->intersected_elements,
+                                            element->data);
+    GNUNET_assert (NULL != se);
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Removed element with key %s and value %lld\n",
+         GNUNET_h2s (&se->key),
+         (long long) GNUNET_ntohll (se->value));
+    GNUNET_assert (GNUNET_YES ==
+                   GNUNET_CONTAINER_multihashmap_remove (
+                     s->intersected_elements,
+                     element->data,
+                     se));
+    GNUNET_free (se);
+    return;
+  case GNUNET_SETI_STATUS_DONE:
+    s->intersection_op = NULL;
+    GNUNET_break (NULL == s->intersection_set);
+    GNUNET_CADET_receive_done (s->channel);
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Finished intersection, %d items remain\n",
+         GNUNET_CONTAINER_multihashmap_size (s->intersected_elements));
+    if (s->client_received_element_count ==
+        GNUNET_CONTAINER_multihashmap_size (s->intersected_elements))
+    {
+      /* CADET transmission from Alice is also already done,
+         start with our own reply */
+      transmit_bobs_cryptodata_message (s);
+    }
+    return;
+  case GNUNET_SETI_STATUS_FAILURE:
+    /* unhandled status code */
+    LOG (GNUNET_ERROR_TYPE_DEBUG,
+         "Set intersection failed!\n");
+    s->intersection_op = NULL;
+    if (NULL != s->intersection_set)
+    {
+      GNUNET_SETI_destroy (s->intersection_set);
+      s->intersection_set = NULL;
+    }
+    s->status = GNUNET_SCALARPRODUCT_STATUS_FAILURE;
+    prepare_client_end_notification (s);
+    return;
+
+  default:
+    GNUNET_break (0);
+    return;
+  }
+}
+
+
+/**
+ * We've paired up a client session with an incoming CADET request.
+ * Initiate set intersection work.
+ *
+ * @param s client session to start intersection for
+ */
+static void
+start_intersection (struct BobServiceSession *s)
+{
+  struct GNUNET_HashCode set_sid;
+
+  GNUNET_CRYPTO_hash (&s->session_id,
+                      sizeof(struct GNUNET_HashCode),
+                      &set_sid);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Got session with key %s and %u elements, starting intersection.\n",
+              GNUNET_h2s (&s->session_id),
+              (unsigned int) s->total);
+
+  s->intersection_op
+    = GNUNET_SETI_prepare (&s->peer,
+                           &set_sid,
+                           NULL,
+                           (struct GNUNET_SETI_Option[]) { { 0 } },
+                           &cb_intersection_element_removed,
+                           s);
+  if (GNUNET_OK !=
+      GNUNET_SETI_commit (s->intersection_op,
+                          s->intersection_set))
+  {
+    GNUNET_break (0);
+    s->status = GNUNET_SCALARPRODUCT_STATUS_FAILURE;
+    prepare_client_end_notification (s);
+    return;
+  }
+  GNUNET_SETI_destroy (s->intersection_set);
+  s->intersection_set = NULL;
+}
+
+
+/**
+ * Handle a request from Alice to calculate a scalarproduct with us (Bob).
+ *
+ * @param cls closure (set from #GNUNET_CADET_connect)
+ * @param msg the actual message
+ */
+static void
+handle_alices_computation_request (void *cls,
+                                   const struct EccServiceRequestMessage *msg)
+{
+  struct BobServiceSession *s = cls;
+
+  s->session_id = msg->session_id; // ??
+  if (s->client_received_element_count < s->total)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Alice ready, still waiting for Bob client data!\n");
+    return;
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Both ready, launching intersection!\n");
+  start_intersection (s);
+}
+
+
+/**
+ * Function called for inbound channels on Bob's end.  Does some
+ * preliminary initialization, more happens after we get Alice's first
+ * message.
+ *
+ * @param cls our `struct BobServiceSession`
+ * @param channel new handle to the channel
+ * @param initiator peer that started the channel
+ * @return session associated with the channel
+ */
+static void *
+cb_channel_incoming (void *cls,
+                     struct GNUNET_CADET_Channel *channel,
+                     const struct GNUNET_PeerIdentity *initiator)
+{
+  struct BobServiceSession *s = cls;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "New incoming channel from peer %s.\n",
+              GNUNET_i2s (initiator));
+  GNUNET_CADET_close_port (s->port);
+  s->port = NULL;
+  s->peer = *initiator;
+  s->channel = channel;
+  s->cadet_mq = GNUNET_CADET_get_mq (s->channel);
+  return s;
+}
+
+
+/**
+ * We're receiving additional set data. Check it is well-formed.
+ *
+ * @param cls identification of the client
+ * @param msg the actual message
+ * @return #GNUNET_OK if @a msg is well-formed
+ */
+static int
+check_bob_client_message_multipart (
+  void *cls,
+  const struct ComputationBobCryptodataMultipartMessage *msg)
+{
+  struct BobServiceSession *s = cls;
+  uint32_t contained_count;
+  uint16_t msize;
+
+  msize = ntohs (msg->header.size);
+  contained_count = ntohl (msg->element_count_contained);
+  if ((msize != (sizeof(struct ComputationBobCryptodataMultipartMessage)
+                 + contained_count * sizeof(struct
+                                            GNUNET_SCALARPRODUCT_Element))) ||
+      (0 == contained_count) ||
+      (UINT16_MAX < contained_count) ||
+      (s->total == s->client_received_element_count) ||
+      (s->total < s->client_received_element_count + contained_count))
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * We're receiving additional set data. Add it to our
+ * set and if we are done, initiate the transaction.
+ *
+ * @param cls identification of the client
+ * @param msg the actual message
+ */
+static void
+handle_bob_client_message_multipart (
+  void *cls,
+  const struct ComputationBobCryptodataMultipartMessage *msg)
+{
+  struct BobServiceSession *s = cls;
+  uint32_t contained_count;
+  const struct GNUNET_SCALARPRODUCT_Element *elements;
+  struct GNUNET_SETI_Element set_elem;
+  struct GNUNET_SCALARPRODUCT_Element *elem;
+
+  contained_count = ntohl (msg->element_count_contained);
+  elements = (const struct GNUNET_SCALARPRODUCT_Element *) &msg[1];
+  for (uint32_t i = 0; i < contained_count; i++)
+  {
+    elem = GNUNET_new (struct GNUNET_SCALARPRODUCT_Element);
+    GNUNET_memcpy (elem,
+                   &elements[i],
+                   sizeof(struct GNUNET_SCALARPRODUCT_Element));
+    if (GNUNET_SYSERR ==
+        GNUNET_CONTAINER_multihashmap_put (s->intersected_elements,
+                                           &elem->key,
+                                           elem,
+                                           GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
+    {
+      GNUNET_break (0);
+      GNUNET_free (elem);
+      continue;
+    }
+    set_elem.data = &elem->key;
+    set_elem.size = sizeof(elem->key);
+    set_elem.element_type = 0;
+    GNUNET_SETI_add_element (s->intersection_set,
+                             &set_elem,
+                             NULL, NULL);
+  }
+  s->client_received_element_count += contained_count;
+  GNUNET_SERVICE_client_continue (s->client);
+  if (s->total != s->client_received_element_count)
+  {
+    /* more to come */
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Request still partial, waiting for more client data!\n");
+    return;
+  }
+  if (NULL == s->channel)
+  {
+    /* no Alice waiting for this request, wait for Alice */
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "Client ready, still waiting for Alice!\n");
+    return;
+  }
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Both ready, launching intersection!\n");
+  start_intersection (s);
+}
+
+
+/**
+ * Handler for Bob's a client request message.  Check @a msg is
+ * well-formed.
+ *
+ * @param cls identification of the client
+ * @param msg the actual message
+ * @return #GNUNET_OK if @a msg is well-formed
+ */
+static int
+check_bob_client_message (void *cls,
+                          const struct BobComputationMessage *msg)
+{
+  struct BobServiceSession *s = cls;
+  uint32_t contained_count;
+  uint32_t total_count;
+  uint16_t msize;
+
+  if (GNUNET_SCALARPRODUCT_STATUS_INIT != s->status)
+  {
+    GNUNET_break (0);
+    return GNUNET_SYSERR;
+  }
+  msize = ntohs (msg->header.size);
+  total_count = ntohl (msg->element_count_total);
+  contained_count = ntohl (msg->element_count_contained);
+  if ((0 == total_count) ||
+      (0 == contained_count) ||
+      (UINT16_MAX < contained_count) ||
+      (msize != (sizeof(struct BobComputationMessage)
+                 + contained_count * sizeof(struct
+                                            GNUNET_SCALARPRODUCT_Element))))
+  {
+    GNUNET_break_op (0);
+    return GNUNET_SYSERR;
+  }
+  return GNUNET_OK;
+}
+
+
+/**
+ * Handler for Bob's a client request message.  Bob is in the response
+ * role, keep the values + session and waiting for a matching session
+ * or process a waiting request from Alice.
+ *
+ * @param cls identification of the client
+ * @param msg the actual message
+ */
+static void
+handle_bob_client_message (void *cls,
+                           const struct BobComputationMessage *msg)
+{
+  struct BobServiceSession *s = cls;
+  struct GNUNET_MQ_MessageHandler cadet_handlers[] = {
+    GNUNET_MQ_hd_fixed_size (alices_computation_request,
+                             GNUNET_MESSAGE_TYPE_SCALARPRODUCT_ECC_SESSION_INITIALIZATION,
+                             struct EccServiceRequestMessage,
+                             s),
+    GNUNET_MQ_hd_var_size (alices_cryptodata_message,
+                           GNUNET_MESSAGE_TYPE_SCALARPRODUCT_ECC_ALICE_CRYPTODATA,
+                           struct EccAliceCryptodataMessage,
+                           s),
+    GNUNET_MQ_handler_end ()
+  };
+  uint32_t contained_count;
+  uint32_t total_count;
+  const struct GNUNET_SCALARPRODUCT_Element *elements;
+  struct GNUNET_SETI_Element set_elem;
+  struct GNUNET_SCALARPRODUCT_Element *elem;
+
+  total_count = ntohl (msg->element_count_total);
+  contained_count = ntohl (msg->element_count_contained);
+
+  s->status = GNUNET_SCALARPRODUCT_STATUS_ACTIVE;
+  s->total = total_count;
+  s->client_received_element_count = contained_count;
+  s->session_id = msg->session_key;
+  elements = (const struct GNUNET_SCALARPRODUCT_Element *) &msg[1];
+  s->intersected_elements
+    = GNUNET_CONTAINER_multihashmap_create (s->total,
+                                            GNUNET_YES);
+  s->intersection_set = GNUNET_SETI_create (cfg);
+  for (uint32_t i = 0; i < contained_count; i++)
+  {
+    if (0 == GNUNET_ntohll (elements[i].value))
+      continue;
+    elem = GNUNET_new (struct GNUNET_SCALARPRODUCT_Element);
+    GNUNET_memcpy (elem,
+                   &elements[i],
+                   sizeof(struct GNUNET_SCALARPRODUCT_Element));
+    if (GNUNET_SYSERR ==
+        GNUNET_CONTAINER_multihashmap_put (s->intersected_elements,
+                                           &elem->key,
+                                           elem,
+                                           GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY))
+    {
+      GNUNET_break (0);
+      GNUNET_free (elem);
+      continue;
+    }
+    set_elem.data = &elem->key;
+    set_elem.size = sizeof(elem->key);
+    set_elem.element_type = 0;
+    GNUNET_SETI_add_element (s->intersection_set,
+                             &set_elem,
+                             NULL, NULL);
+    s->used_element_count++;
+  }
+  GNUNET_SERVICE_client_continue (s->client);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Received client request, opening port %s!\n",
+              GNUNET_h2s (&msg->session_key));
+  s->port = GNUNET_CADET_open_port (my_cadet,
+                                    &msg->session_key,
+                                    &cb_channel_incoming,
+                                    s,
+                                    NULL,
+                                    &cb_channel_destruction,
+                                    cadet_handlers);
+  if (NULL == s->port)
+  {
+    GNUNET_break (0);
+    GNUNET_SERVICE_client_drop (s->client);
+    return;
+  }
+}
+
+
+/**
+ * Task run during shutdown.
+ *
+ * @param cls unused
+ */
+static void
+shutdown_task (void *cls)
+{
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Shutting down, initiating cleanup.\n");
+  // FIXME: we have to cut our connections to CADET first!
+  if (NULL != my_cadet)
+  {
+    GNUNET_CADET_disconnect (my_cadet);
+    my_cadet = NULL;
+  }
+  if (NULL != edc)
+  {
+    GNUNET_CRYPTO_ecc_dlog_release (edc);
+    edc = NULL;
+  }
+}
+
+
+/**
+ * A client connected.
+ *
+ * Setup the associated data structure.
+ *
+ * @param cls closure, NULL
+ * @param client identification of the client
+ * @param mq message queue to communicate with @a client
+ * @return our `struct BobServiceSession`
+ */
+static void *
+client_connect_cb (void *cls,
+                   struct GNUNET_SERVICE_Client *client,
+                   struct GNUNET_MQ_Handle *mq)
+{
+  struct BobServiceSession *s;
+
+  s = GNUNET_new (struct BobServiceSession);
+  s->client = client;
+  s->client_mq = mq;
+  return s;
+}
+
+
+/**
+ * A client disconnected.
+ *
+ * Remove the associated session(s), release data structures
+ * and cancel pending outgoing transmissions to the client.
+ *
+ * @param cls closure, NULL
+ * @param client identification of the client
+ * @param app_cls our `struct BobServiceSession`
+ */
+static void
+client_disconnect_cb (void *cls,
+                      struct GNUNET_SERVICE_Client *client,
+                      void *app_cls)
+{
+  struct BobServiceSession *s = app_cls;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "Client disconnected from us.\n");
+  s->client = NULL;
+  destroy_service_session (s);
+}
+
+
+/**
+ * Initialization of the program and message handlers
+ *
+ * @param cls closure
+ * @param c configuration to use
+ * @param service the initialized service
+ */
+static void
+run (void *cls,
+     const struct GNUNET_CONFIGURATION_Handle *c,
+     struct GNUNET_SERVICE_Handle *service)
+{
+  cfg = c;
+  /* We don't really do DLOG, so we can setup with very minimal resources */
+  edc = GNUNET_CRYPTO_ecc_dlog_prepare (4 /* max value */,
+                                        2 /* RAM */);
+  my_cadet = GNUNET_CADET_connect (cfg);
+  GNUNET_SCHEDULER_add_shutdown (&shutdown_task,
+                                 NULL);
+  if (NULL == my_cadet)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
+                _ ("Connect to CADET failed\n"));
+    GNUNET_SCHEDULER_shutdown ();
+    return;
+  }
+}
+
+
+/**
+ * Define "main" method using service macro.
+ */
+GNUNET_SERVICE_MAIN
+  ("scalarproduct-bob",
+  GNUNET_SERVICE_OPTION_NONE,
+  &run,
+  &client_connect_cb,
+  &client_disconnect_cb,
+  NULL,
+  GNUNET_MQ_hd_var_size (bob_client_message,
+                         GNUNET_MESSAGE_TYPE_SCALARPRODUCT_CLIENT_TO_BOB,
+                         struct BobComputationMessage,
+                         NULL),
+  GNUNET_MQ_hd_var_size (bob_client_message_multipart,
+                         GNUNET_MESSAGE_TYPE_SCALARPRODUCT_CLIENT_MULTIPART_BOB,
+                         struct ComputationBobCryptodataMultipartMessage,
+                         NULL),
+  GNUNET_MQ_handler_end ());
+
+
+/* end of gnunet-service-scalarproduct-ecc_bob.c */