2 This file is part of GNUnet.
3 (C) 2013 Christian Grothoff (and other contributing authors)
5 GNUnet is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published
7 by the Free Software Foundation; either version 3, or (at your
8 option) any later version.
10 GNUnet is distributed in the hope that it will be useful, but
11 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with GNUnet; see the file COPYING. If not, write to the
17 Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA.
22 * @file secretsharing/gnunet-service-secretsharing.c
23 * @brief secret sharing service
24 * @author Florian Dold
27 #include "gnunet_util_lib.h"
28 #include "gnunet_time_lib.h"
29 #include "gnunet_signatures.h"
30 #include "gnunet_consensus_service.h"
31 #include "secretsharing.h"
32 #include "secretsharing_protocol.h"
36 #define EXTRA_CHECKS 1
40 * Info about a peer in a key generation session.
45 * Peer identity of the peer.
47 struct GNUNET_PeerIdentity peer;
50 * The peer's paillier public key.
51 * Freshly generated for each keygen session.
53 struct GNUNET_CRYPTO_PaillierPublicKey paillier_public_key;
56 * The peer's commitment to his presecret.
58 gcry_mpi_t presecret_commitment;
61 * Commitment to the preshare that is
62 * intended for our peer.
64 gcry_mpi_t preshare_commitment;
67 * Sigma (exponentiated share) for this peer.
72 * Did we successfully receive the round1 element
78 * Did we successfully receive the round2 element
86 * Information about a peer in a decrypt session.
88 struct DecryptPeerInfo
91 * Identity of the peer.
93 struct GNUNET_PeerIdentity peer;
96 * Original index in the key generation round.
97 * Necessary for computing the lagrange coefficients.
99 unsigned int original_index;
102 * Set to the partial decryption of
103 * this peer, or NULL if we did not
104 * receive a partial decryption from this
105 * peer or the zero knowledge proof failed.
107 gcry_mpi_t partial_decryption;
112 * Session to establish a threshold-shared secret.
117 * Keygen sessions are held in a linked list.
119 struct KeygenSession *next;
122 * Keygen sessions are held in a linked list.
124 struct KeygenSession *prev;
127 * Current consensus, used for both DKG rounds.
129 struct GNUNET_CONSENSUS_Handle *consensus;
132 * Client that is interested in the result
133 * of this key generation session.
135 struct GNUNET_SERVER_Client *client;
138 * Message queue for 'client'
140 struct GNUNET_MQ_Handle *client_mq;
143 * Randomly generated coefficients of the polynomial for sharing our
144 * pre-secret, where 'preshares[0]' is our pre-secret. Contains 'threshold'
145 * elements, thus represents a polynomial of degree 'threshold-1', which can
146 * be interpolated with 'threshold' data points.
148 * The pre-secret-shares 'i=1,...,num_peers' are given by evaluating this
149 * polyomial at 'i' for share i.
151 gcry_mpi_t *presecret_polynomial;
154 * Minimum number of shares required to restore the secret.
155 * Also the number of coefficients for the polynomial representing
156 * the sharing. Obviously, the polynomial then has degree threshold-1.
158 unsigned int threshold;
161 * Total number of peers.
163 unsigned int num_peers;
166 * Index of the local peer.
168 unsigned int local_peer;
171 * Information about all participating peers.
172 * Array of size 'num_peers'.
174 struct KeygenPeerInfo *info;
177 * List of all peers involved in the secret sharing session.
179 struct GNUNET_PeerIdentity *peers;
182 * Identifier for this session.
184 struct GNUNET_HashCode session_id;
187 * Paillier private key of our peer.
189 struct GNUNET_CRYPTO_PaillierPrivateKey paillier_private_key;
192 * When would we like the key to be established?
194 struct GNUNET_TIME_Absolute deadline;
197 * When does the DKG start? Necessary to compute fractions of the
198 * operation's desired time interval.
200 struct GNUNET_TIME_Absolute start_time;
203 * Index of the local peer in the ordered list
204 * of peers in the session.
206 unsigned int local_peer_idx;
209 * Share of our peer. Once preshares from other peers are received, they
210 * will be added to 'my'share.
215 * Public key, will be updated when a round2 element arrives.
217 gcry_mpi_t public_key;
222 * Session to cooperatively decrypt a value.
224 struct DecryptSession
227 * Decrypt sessions are stored in a linked list.
229 struct DecryptSession *next;
232 * Decrypt sessions are stored in a linked list.
234 struct DecryptSession *prev;
237 * Handle to the consensus over partial decryptions.
239 struct GNUNET_CONSENSUS_Handle *consensus;
242 * Client connected to us.
244 struct GNUNET_SERVER_Client *client;
247 * Message queue for 'client'.
249 struct GNUNET_MQ_Handle *client_mq;
252 * When should we start communicating for decryption?
254 struct GNUNET_TIME_Absolute start;
257 * When would we like the ciphertext to be
260 struct GNUNET_TIME_Absolute deadline;
263 * Ciphertext we want to decrypt.
265 struct GNUNET_SECRETSHARING_Ciphertext ciphertext;
268 * Share of the local peer.
269 * Containts other important information, such as
270 * the list of other peers.
272 struct GNUNET_SECRETSHARING_Share *share;
275 * State information about other peers.
277 struct DecryptPeerInfo *info;
282 * Decrypt sessions are held in a linked list.
284 static struct DecryptSession *decrypt_sessions_head;
287 * Decrypt sessions are held in a linked list.
289 static struct DecryptSession *decrypt_sessions_tail;
292 * Decrypt sessions are held in a linked list.
294 static struct KeygenSession *keygen_sessions_head;
297 * Decrypt sessions are held in a linked list.
299 static struct KeygenSession *keygen_sessions_tail;
302 * The ElGamal prime field order as libgcrypt mpi.
303 * Initialized in #init_crypto_constants.
305 static gcry_mpi_t elgamal_q;
308 * Modulus of the prime field used for ElGamal.
309 * Initialized in #init_crypto_constants.
311 static gcry_mpi_t elgamal_p;
314 * Generator for prime field of order 'elgamal_q'.
315 * Initialized in #init_crypto_constants.
317 static gcry_mpi_t elgamal_g;
320 * Peer that runs this service.
322 static struct GNUNET_PeerIdentity my_peer;
325 * Peer that runs this service.
327 static struct GNUNET_CRYPTO_EddsaPrivateKey *my_peer_private_key;
330 * Configuration of this service.
332 static const struct GNUNET_CONFIGURATION_Handle *cfg;
335 * Server for this service.
337 static struct GNUNET_SERVER_Handle *srv;
341 * Get the peer info belonging to a peer identity in a keygen session.
343 * @param ks The keygen session.
344 * @param peer The peer identity.
345 * @return The Keygen peer info, or NULL if the peer could not be found.
347 static struct KeygenPeerInfo *
348 get_keygen_peer_info (const struct KeygenSession *ks,
349 const struct GNUNET_PeerIdentity *peer)
352 for (i = 0; i < ks->num_peers; i++)
353 if (0 == memcmp (peer, &ks->info[i].peer, sizeof (struct GNUNET_PeerIdentity)))
360 * Get the peer info belonging to a peer identity in a decrypt session.
362 * @param ds The decrypt session.
363 * @param peer The peer identity.
364 * @return The decrypt peer info, or NULL if the peer could not be found.
366 static struct DecryptPeerInfo *
367 get_decrypt_peer_info (const struct DecryptSession *ds,
368 const struct GNUNET_PeerIdentity *peer)
371 for (i = 0; i < ds->share->num_peers; i++)
372 if (0 == memcmp (peer, &ds->info[i].peer, sizeof (struct GNUNET_PeerIdentity)))
379 * Interpolate between two points in time.
381 * @param start start time
382 * @param end end time
383 * @param num numerator of the scale factor
384 * @param denum denumerator of the scale factor
386 static struct GNUNET_TIME_Absolute
387 time_between (struct GNUNET_TIME_Absolute start,
388 struct GNUNET_TIME_Absolute end,
391 struct GNUNET_TIME_Absolute result;
394 GNUNET_assert (start.abs_value_us <= end.abs_value_us);
395 diff = end.abs_value_us - start.abs_value_us;
396 result.abs_value_us = start.abs_value_us + ((diff * num) / denum);
403 * Compare two peer identities. Indended to be used with qsort or bsearch.
405 * @param p1 Some peer identity.
406 * @param p2 Some peer identity.
407 * @return 1 if p1 > p2, -1 if p1 < p2 and 0 if p1 == p2.
410 peer_id_cmp (const void *p1, const void *p2)
412 return memcmp (p1, p2, sizeof (struct GNUNET_PeerIdentity));
417 * Get the index of a peer in an array of peers
419 * @param haystack Array of peers.
420 * @param n Size of @a haystack.
421 * @param needle Peer to find
422 * @return Index of @a needle in @a haystack, or -1 if peer
423 * is not in the list.
426 peer_find (const struct GNUNET_PeerIdentity *haystack, unsigned int n,
427 const struct GNUNET_PeerIdentity *needle)
430 for (i = 0; i < n; i++)
431 if (0 == memcmp (&haystack[i], needle, sizeof (struct GNUNET_PeerIdentity)))
438 * Normalize the given list of peers, by including the local peer
439 * (if it is missing) and sorting the peers by their identity.
441 * @param listed Peers in the unnormalized list.
442 * @param num_listed Peers in the un-normalized list.
443 * @param[out] num_normalized Number of peers in the normalized list.
444 * @param[out] my_peer_idx Index of the local peer in the normalized list.
445 * @return Normalized list, must be free'd by the caller.
447 static struct GNUNET_PeerIdentity *
448 normalize_peers (struct GNUNET_PeerIdentity *listed,
449 unsigned int num_listed,
450 unsigned int *num_normalized,
451 unsigned int *my_peer_idx)
453 unsigned int local_peer_in_list;
454 /* number of peers in the normalized list */
456 struct GNUNET_PeerIdentity *normalized;
458 local_peer_in_list = GNUNET_YES;
460 if (peer_find (listed, num_listed, &my_peer) < 0)
462 local_peer_in_list = GNUNET_NO;
466 normalized = GNUNET_new_array (n, struct GNUNET_PeerIdentity);
468 if (GNUNET_NO == local_peer_in_list)
469 normalized[n - 1] = my_peer;
471 memcpy (normalized, listed, num_listed * sizeof (struct GNUNET_PeerIdentity));
472 qsort (normalized, n, sizeof (struct GNUNET_PeerIdentity), &peer_id_cmp);
474 if (NULL != my_peer_idx)
475 *my_peer_idx = peer_find (normalized, n, &my_peer);
476 if (NULL != num_normalized)
484 * Get a the j-th lagrange coefficient for a set of indices.
486 * @param[out] coeff the lagrange coefficient
487 * @param j lagrange coefficient we want to compute
488 * @param indices indices
489 * @param num number of indices in @a indices
492 compute_lagrange_coefficient (gcry_mpi_t coeff, unsigned int j,
493 unsigned int *indices,
501 /* temp value for l-j */
504 GNUNET_assert (0 != coeff);
506 GNUNET_assert (0 != (n = gcry_mpi_new (0)));
507 GNUNET_assert (0 != (d = gcry_mpi_new (0)));
508 GNUNET_assert (0 != (tmp = gcry_mpi_new (0)));
510 gcry_mpi_set_ui (n, 1);
511 gcry_mpi_set_ui (d, 1);
513 for (i = 0; i < num; i++)
515 unsigned int l = indices[i];
518 gcry_mpi_mul_ui (n, n, l + 1);
520 gcry_mpi_set_ui (tmp, l + 1);
521 gcry_mpi_sub_ui (tmp, tmp, j + 1);
522 gcry_mpi_mul (d, d, tmp);
525 // gcry_mpi_invm does not like negative numbers ...
526 gcry_mpi_mod (d, d, elgamal_q);
528 GNUNET_assert (gcry_mpi_cmp_ui (d, 0) > 0);
530 // now we do the actual division, with everything mod q, as we
531 // are not operating on elements from <g>, but on exponents
532 GNUNET_assert (0 != gcry_mpi_invm (d, d, elgamal_q));
534 gcry_mpi_mulm (coeff, n, d, elgamal_q);
536 gcry_mpi_release (n);
537 gcry_mpi_release (d);
538 gcry_mpi_release (tmp);
543 * Destroy a decrypt session, removing it from
544 * the linked list of decrypt sessions.
546 * @param ds decrypt session to destroy
549 decrypt_session_destroy (struct DecryptSession *ds)
551 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "destroying decrypt session\n");
553 GNUNET_CONTAINER_DLL_remove (decrypt_sessions_head, decrypt_sessions_tail, ds);
555 if (NULL != ds->consensus)
557 GNUNET_CONSENSUS_destroy (ds->consensus);
558 ds->consensus = NULL;
561 if (NULL != ds->info)
564 for (i = 0; i < ds->share->num_peers; i++)
566 if (NULL != ds->info[i].partial_decryption)
568 gcry_mpi_release (ds->info[i].partial_decryption);
569 ds->info[i].partial_decryption = NULL;
572 GNUNET_free (ds->info);
576 if (NULL != ds->share)
578 GNUNET_SECRETSHARING_share_destroy (ds->share);
582 if (NULL != ds->client_mq)
584 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "destroying decrypt MQ\n");
585 GNUNET_MQ_destroy (ds->client_mq);
586 ds->client_mq = NULL;
589 if (NULL != ds->client)
591 GNUNET_SERVER_client_disconnect (ds->client);
599 keygen_info_destroy (struct KeygenPeerInfo *info)
601 if (NULL != info->sigma)
603 gcry_mpi_release (info->sigma);
606 if (NULL != info->presecret_commitment)
608 gcry_mpi_release (info->presecret_commitment);
609 info->presecret_commitment = NULL;
611 if (NULL != info->preshare_commitment)
613 gcry_mpi_release (info->preshare_commitment);
614 info->presecret_commitment = NULL;
620 keygen_session_destroy (struct KeygenSession *ks)
622 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "destroying keygen session\n");
624 GNUNET_CONTAINER_DLL_remove (keygen_sessions_head, keygen_sessions_tail, ks);
626 if (NULL != ks->info)
629 for (i = 0; i < ks->num_peers; i++)
630 keygen_info_destroy (&ks->info[i]);
631 GNUNET_free (ks->info);
635 if (NULL != ks->consensus)
637 GNUNET_CONSENSUS_destroy (ks->consensus);
638 ks->consensus = NULL;
641 if (NULL != ks->presecret_polynomial)
644 for (i = 0; i < ks->threshold; i++)
646 GNUNET_assert (NULL != ks->presecret_polynomial[i]);
647 gcry_mpi_release (ks->presecret_polynomial[i]);
648 ks->presecret_polynomial[i] = NULL;
650 GNUNET_free (ks->presecret_polynomial);
651 ks->presecret_polynomial = NULL;
654 if (NULL != ks->client_mq)
656 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "destroying keygen MQ\n");
657 GNUNET_MQ_destroy (ks->client_mq);
658 ks->client_mq = NULL;
661 if (NULL != ks->my_share)
663 gcry_mpi_release (ks->my_share);
667 if (NULL != ks->public_key)
669 gcry_mpi_release (ks->public_key);
670 ks->public_key = NULL;
673 if (NULL != ks->peers)
675 GNUNET_free (ks->peers);
679 if (NULL != ks->client)
681 GNUNET_SERVER_client_disconnect (ks->client);
690 * Task run during shutdown.
696 cleanup_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
698 while (NULL != decrypt_sessions_head)
699 decrypt_session_destroy (decrypt_sessions_head);
701 while (NULL != keygen_sessions_head)
702 keygen_session_destroy (keygen_sessions_head);
708 * Generate the random coefficients of our pre-secret polynomial
710 * @param ks the session
713 generate_presecret_polynomial (struct KeygenSession *ks)
718 GNUNET_assert (NULL == ks->presecret_polynomial);
719 ks->presecret_polynomial = GNUNET_new_array (ks->threshold, gcry_mpi_t);
720 for (i = 0; i < ks->threshold; i++)
722 v = ks->presecret_polynomial[i] = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS);
723 GNUNET_assert (NULL != v);
724 // Randomize v such that 0 < v < elgamal_q.
725 // The '- 1' is necessary as bitlength(q) = bitlength(p) - 1.
728 gcry_mpi_randomize (v, GNUNET_SECRETSHARING_ELGAMAL_BITS - 1, GCRY_WEAK_RANDOM);
729 } while ((gcry_mpi_cmp_ui (v, 0) == 0) || (gcry_mpi_cmp (v, elgamal_q) >= 0));
735 * Consensus element handler for round one.
736 * We should get one ephemeral key for each peer.
738 * @param cls Closure (keygen session).
739 * @param element The element from consensus, or
740 * NULL if consensus failed.
743 keygen_round1_new_element (void *cls,
744 const struct GNUNET_SET_Element *element)
746 const struct GNUNET_SECRETSHARING_KeygenCommitData *d;
747 struct KeygenSession *ks = cls;
748 struct KeygenPeerInfo *info;
752 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "round1 consensus failed\n");
756 /* elements have fixed size */
757 if (element->size != sizeof (struct GNUNET_SECRETSHARING_KeygenCommitData))
759 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
760 "keygen commit data with wrong size (%u) in consensus, "
762 element->size, sizeof (struct GNUNET_SECRETSHARING_KeygenCommitData));
766 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "got round1 element\n");
769 info = get_keygen_peer_info (ks, &d->peer);
773 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong peer identity (%s) in consensus\n",
774 GNUNET_i2s (&d->peer));
778 /* Check that the right amount of data has been signed. */
779 if (d->purpose.size !=
780 htonl (element->size - offsetof (struct GNUNET_SECRETSHARING_KeygenCommitData, purpose)))
782 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong signature purpose size in consensus\n");
786 if (GNUNET_OK != GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG1,
787 &d->purpose, &d->signature, &d->peer.public_key))
789 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with invalid signature in consensus\n");
792 info->paillier_public_key = d->pubkey;
793 GNUNET_CRYPTO_mpi_scan_unsigned (&info->presecret_commitment, &d->commitment, 512 / 8);
794 info->round1_valid = GNUNET_YES;
799 * Evaluate the polynomial with coefficients @a coeff at @a x.
800 * The i-th element in @a coeff corresponds to the coefficient of x^i.
802 * @param[out] z result of the evaluation
803 * @param coeff array of coefficients
804 * @param num_coeff number of coefficients
805 * @param x where to evaluate the polynomial
806 * @param m what group are we operating in?
809 horner_eval (gcry_mpi_t z, gcry_mpi_t *coeff, unsigned int num_coeff, gcry_mpi_t x, gcry_mpi_t m)
813 gcry_mpi_set_ui (z, 0);
814 for (i = 0; i < num_coeff; i++)
817 gcry_mpi_mul (z, z, x);
818 gcry_mpi_addm (z, z, coeff[num_coeff - i - 1], m);
824 keygen_round2_conclude (void *cls)
826 struct KeygenSession *ks = cls;
827 struct GNUNET_SECRETSHARING_SecretReadyMessage *m;
828 struct GNUNET_MQ_Envelope *ev;
832 struct GNUNET_SECRETSHARING_Share *share;
834 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "round2 conclude\n");
836 GNUNET_CONSENSUS_destroy (ks->consensus);
837 ks->consensus = NULL;
839 share = GNUNET_new (struct GNUNET_SECRETSHARING_Share);
841 share->num_peers = 0;
843 for (i = 0; i < ks->num_peers; i++)
844 if (GNUNET_YES == ks->info[i].round2_valid)
847 share->peers = GNUNET_new_array (share->num_peers, struct GNUNET_PeerIdentity);
849 GNUNET_new_array (share->num_peers, struct GNUNET_SECRETSHARING_FieldElement);
850 share->original_indices = GNUNET_new_array (share->num_peers, uint16_t);
852 /* maybe we're not even in the list of peers? */
853 share->my_peer = share->num_peers;
855 j = 0; /* running index of valid peers */
856 for (i = 0; i < ks->num_peers; i++)
858 if (GNUNET_YES == ks->info[i].round2_valid)
860 share->peers[j] = ks->info[i].peer;
861 GNUNET_CRYPTO_mpi_print_unsigned (&share->sigmas[j],
862 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
864 share->original_indices[i] = j;
865 if (0 == memcmp (&share->peers[i], &my_peer, sizeof (struct GNUNET_PeerIdentity)))
871 if (share->my_peer == share->num_peers)
873 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: peer identity not in share\n", ks->local_peer_idx);
876 GNUNET_CRYPTO_mpi_print_unsigned (&share->my_share, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
878 GNUNET_CRYPTO_mpi_print_unsigned (&share->public_key, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
881 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "keygen completed with %u peers\n", share->num_peers);
883 /* Write the share. If 0 peers completed the dkg, an empty
884 * share will be sent. */
886 GNUNET_assert (GNUNET_OK == GNUNET_SECRETSHARING_share_write (share, NULL, 0, &share_size));
888 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "writing share of size %u\n",
889 (unsigned int) share_size);
891 ev = GNUNET_MQ_msg_extra (m, share_size,
892 GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_SECRET_READY);
894 GNUNET_assert (GNUNET_OK == GNUNET_SECRETSHARING_share_write (share, &m[1], share_size, NULL));
896 GNUNET_SECRETSHARING_share_destroy (share);
899 GNUNET_MQ_send (ks->client_mq, ev);
904 * Insert round 2 element in the consensus, consisting of
905 * (1) The exponentiated pre-share polynomial coefficients A_{i,l}=g^{a_{i,l}}
906 * (2) The exponentiated pre-shares y_{i,j}=g^{s_{i,j}}
907 * (3) The encrypted pre-shares Y_{i,j}
908 * (4) The zero knowledge proof for fairness of
911 * @param ks session to use
914 insert_round2_element (struct KeygenSession *ks)
916 struct GNUNET_SET_Element *element;
917 struct GNUNET_SECRETSHARING_KeygenRevealData *d;
919 unsigned char *last_pos;
925 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting round2 element\n",
928 GNUNET_assert (NULL != (v = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
929 GNUNET_assert (NULL != (idx = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
931 element_size = (sizeof (struct GNUNET_SECRETSHARING_KeygenRevealData) +
932 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->num_peers +
933 sizeof (struct GNUNET_CRYPTO_PaillierCiphertext) * ks->num_peers +
934 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->threshold);
936 element = GNUNET_malloc (sizeof (struct GNUNET_SET_Element) + element_size);
937 element->size = element_size;
938 element->data = (void *) &element[1];
940 d = (void *) element->data;
943 // start inserting vector elements
944 // after the fixed part of the element's data
945 pos = (void *) &d[1];
946 last_pos = pos + element_size;
948 // exponentiated pre-shares
949 for (i = 0; i < ks->num_peers; i++)
951 ptrdiff_t remaining = last_pos - pos;
952 GNUNET_assert (remaining > 0);
953 gcry_mpi_set_ui (idx, i + 1);
954 // evaluate the polynomial
955 horner_eval (v, ks->presecret_polynomial, ks->threshold, idx, elgamal_q);
956 // take g to the result
957 gcry_mpi_powm (v, elgamal_g, v, elgamal_p);
958 GNUNET_CRYPTO_mpi_print_unsigned (pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
959 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8;
962 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed exp preshares\n",
965 // encrypted pre-shares
966 for (i = 0; i < ks->num_peers; i++)
968 ptrdiff_t remaining = last_pos - pos;
969 struct GNUNET_CRYPTO_PaillierCiphertext *ciphertext;
971 GNUNET_assert (remaining > 0);
972 ciphertext = (void *) pos;
973 memset (ciphertext, 0, sizeof *ciphertext);
974 if (GNUNET_YES == ks->info[i].round1_valid)
976 gcry_mpi_set_ui (idx, i + 1);
977 // evaluate the polynomial
978 horner_eval (v, ks->presecret_polynomial, ks->threshold, idx, elgamal_q);
979 // encrypt the result
980 GNUNET_CRYPTO_paillier_encrypt (&ks->info[i].paillier_public_key, v, 0, ciphertext);
982 pos += sizeof *ciphertext;
985 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed enc preshares\n",
988 // exponentiated coefficients
989 for (i = 0; i < ks->threshold; i++)
991 ptrdiff_t remaining = last_pos - pos;
992 GNUNET_assert (remaining > 0);
993 gcry_mpi_powm (v, elgamal_g, ks->presecret_polynomial[i], elgamal_p);
994 GNUNET_CRYPTO_mpi_print_unsigned (pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
995 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8;
998 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed exp coefficients\n",
1001 d->purpose.size = htonl (element_size - offsetof (struct GNUNET_SECRETSHARING_KeygenRevealData, purpose));
1002 d->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG2);
1003 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key, &d->purpose, &d->signature);
1005 GNUNET_CONSENSUS_insert (ks->consensus, element, NULL, NULL);
1006 GNUNET_free (element); /* FIXME: maybe stack-allocate instead? */
1008 gcry_mpi_release (v);
1009 gcry_mpi_release (idx);
1014 keygen_reveal_get_exp_preshare (struct KeygenSession *ks,
1015 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1019 gcry_mpi_t exp_preshare;
1021 GNUNET_assert (idx < ks->num_peers);
1023 pos = (void *) &d[1];
1024 // skip exponentiated pre-shares we don't want
1025 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * idx;
1026 GNUNET_CRYPTO_mpi_scan_unsigned (&exp_preshare, pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1027 return exp_preshare;
1031 keygen_reveal_get_exp_coeff (struct KeygenSession *ks,
1032 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1036 gcry_mpi_t exp_coeff;
1038 GNUNET_assert (idx < ks->threshold);
1040 pos = (void *) &d[1];
1041 // skip exponentiated pre-shares
1042 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->num_peers;
1043 // skip encrypted pre-shares
1044 pos += sizeof (struct GNUNET_CRYPTO_PaillierCiphertext) * ks->num_peers;
1045 // skip exp. coeffs we are not interested in
1046 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * idx;
1047 // the first exponentiated coefficient is the public key share
1048 GNUNET_CRYPTO_mpi_scan_unsigned (&exp_coeff, pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1053 static struct GNUNET_CRYPTO_PaillierCiphertext *
1054 keygen_reveal_get_enc_preshare (struct KeygenSession *ks,
1055 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1060 GNUNET_assert (idx < ks->num_peers);
1062 pos = (void *) &d[1];
1063 // skip exponentiated pre-shares
1064 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->num_peers;
1065 // skip encrypted pre-shares we're not interested in
1066 pos += sizeof (struct GNUNET_CRYPTO_PaillierCiphertext) * idx;
1067 return (struct GNUNET_CRYPTO_PaillierCiphertext *) pos;
1072 keygen_round2_new_element (void *cls,
1073 const struct GNUNET_SET_Element *element)
1075 struct KeygenSession *ks = cls;
1076 const struct GNUNET_SECRETSHARING_KeygenRevealData *d;
1077 struct KeygenPeerInfo *info;
1078 size_t expected_element_size;
1082 gcry_mpi_t public_key_share;
1083 gcry_mpi_t preshare;
1085 if (NULL == element)
1087 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "round2 consensus failed\n");
1091 expected_element_size = (sizeof (struct GNUNET_SECRETSHARING_KeygenRevealData) +
1092 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->num_peers +
1093 sizeof (struct GNUNET_CRYPTO_PaillierCiphertext) * ks->num_peers +
1094 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->threshold);
1096 if (element->size != expected_element_size)
1098 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1099 "keygen round2 data with wrong size (%u) in consensus, "
1101 element->size, expected_element_size);
1105 d = (const void *) element->data;
1107 info = get_keygen_peer_info (ks, &d->peer);
1111 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong peer identity (%s) in consensus\n",
1112 GNUNET_i2s (&d->peer));
1116 if (GNUNET_NO == info->round1_valid)
1118 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1119 "ignoring round2 element from peer with invalid round1 element (%s)\n",
1120 GNUNET_i2s (&d->peer));
1124 if (GNUNET_YES == info->round2_valid)
1126 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1127 "ignoring duplicate round2 element (%s)\n",
1128 GNUNET_i2s (&d->peer));
1132 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "got round2 element\n");
1134 if (ntohl (d->purpose.size) !=
1135 element->size - offsetof (struct GNUNET_SECRETSHARING_KeygenRevealData, purpose))
1137 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen reveal data with wrong signature purpose size in consensus\n");
1141 if (GNUNET_OK != GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG2,
1142 &d->purpose, &d->signature, &d->peer.public_key))
1144 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen reveal data with invalid signature in consensus\n");
1148 public_key_share = keygen_reveal_get_exp_coeff (ks, d, 0);
1149 info->preshare_commitment = keygen_reveal_get_exp_preshare (ks, d, ks->local_peer_idx);
1151 if (NULL == ks->public_key)
1153 GNUNET_assert (NULL != (ks->public_key = gcry_mpi_new (0)));
1154 gcry_mpi_set_ui (ks->public_key, 1);
1156 gcry_mpi_mulm (ks->public_key, ks->public_key, public_key_share, elgamal_p);
1158 gcry_mpi_release (public_key_share);
1159 public_key_share = NULL;
1161 GNUNET_assert (NULL != (preshare = gcry_mpi_new (0)));
1162 GNUNET_CRYPTO_paillier_decrypt (&ks->paillier_private_key,
1163 &ks->info[ks->local_peer_idx].paillier_public_key,
1164 keygen_reveal_get_enc_preshare (ks, d, ks->local_peer_idx),
1167 GNUNET_assert (NULL != (tmp = gcry_mpi_new (0)));
1168 gcry_mpi_powm (tmp, elgamal_g, preshare, elgamal_p);
1170 // TODO: restore a valid secret from the decryption (the hard part, solving SVP with gauss)
1171 cmp_result = gcry_mpi_cmp (tmp, info->preshare_commitment);
1172 gcry_mpi_release (tmp);
1174 if (0 != cmp_result)
1176 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: Got invalid presecret from P%u\n",
1177 (unsigned int) ks->local_peer_idx, (unsigned int) (info - ks->info));
1181 if (NULL == ks->my_share)
1183 GNUNET_assert (NULL != (ks->my_share = gcry_mpi_new (0)));
1185 gcry_mpi_addm (ks->my_share, ks->my_share, preshare, elgamal_q);
1187 for (j = 0; j < ks->num_peers; j++)
1189 gcry_mpi_t presigma;
1190 if (NULL == ks->info[j].sigma)
1192 GNUNET_assert (NULL != (ks->info[j].sigma = gcry_mpi_new (0)));
1193 gcry_mpi_set_ui (ks->info[j].sigma, 1);
1195 presigma = keygen_reveal_get_exp_preshare (ks, d, j);
1196 gcry_mpi_mulm (ks->info[j].sigma, ks->info[j].sigma, presigma, elgamal_p);
1197 gcry_mpi_release (presigma);
1201 GNUNET_assert (NULL != (prod = gcry_mpi_new (0)));
1203 GNUNET_assert (NULL != (j_to_k = gcry_mpi_new (0)));
1204 // validate that the polynomial sharing matches the additive sharing
1205 for (j = 0; j < ks->num_peers; j++)
1209 gcry_mpi_t exp_preshare;
1210 gcry_mpi_set_ui (prod, 1);
1211 for (k = 0; k < ks->threshold; k++)
1213 // Using pow(double,double) is a bit sketchy.
1214 // We count players from 1, but shares from 0.
1216 gcry_mpi_set_ui (j_to_k, (unsigned int) pow(j+1, k));
1217 tmp = keygen_reveal_get_exp_coeff (ks, d, k);
1218 gcry_mpi_powm (tmp, tmp, j_to_k, elgamal_p);
1219 gcry_mpi_mulm (prod, prod, tmp, elgamal_p);
1220 gcry_mpi_release (tmp);
1222 exp_preshare = keygen_reveal_get_exp_preshare (ks, d, j);
1223 gcry_mpi_mod (exp_preshare, exp_preshare, elgamal_p);
1224 cmp_result = gcry_mpi_cmp (prod, exp_preshare);
1225 gcry_mpi_release (exp_preshare);
1226 exp_preshare = NULL;
1227 if (0 != cmp_result)
1229 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: reveal data from P%u incorrect\n",
1230 ks->local_peer_idx, j);
1231 /* no need for further verification, round2 stays invalid ... */
1236 // TODO: verify proof of fair encryption (once implemented)
1238 info->round2_valid = GNUNET_YES;
1240 gcry_mpi_release (preshare);
1241 gcry_mpi_release (prod);
1242 gcry_mpi_release (j_to_k);
1247 * Called when the first consensus round has concluded.
1248 * Will initiate the second round.
1250 * @param cls closure
1253 keygen_round1_conclude (void *cls)
1255 struct KeygenSession *ks = cls;
1257 GNUNET_CONSENSUS_destroy (ks->consensus);
1259 ks->consensus = GNUNET_CONSENSUS_create (cfg, ks->num_peers, ks->peers, &ks->session_id,
1260 time_between (ks->start_time, ks->deadline, 1, 2),
1262 keygen_round2_new_element, ks);
1264 insert_round2_element (ks);
1266 GNUNET_CONSENSUS_conclude (ks->consensus,
1267 keygen_round2_conclude,
1273 * Insert the ephemeral key and the presecret commitment
1274 * of this peer in the consensus of the given session.
1276 * @param ks session to use
1279 insert_round1_element (struct KeygenSession *ks)
1281 struct GNUNET_SET_Element *element;
1282 struct GNUNET_SECRETSHARING_KeygenCommitData *d;
1285 // big-endian representation of 'v'
1286 unsigned char v_data[GNUNET_SECRETSHARING_ELGAMAL_BITS / 8];
1288 element = GNUNET_malloc (sizeof *element + sizeof *d);
1289 d = (void *) &element[1];
1291 element->size = sizeof *d;
1295 GNUNET_assert (0 != (v = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
1297 gcry_mpi_powm (v, elgamal_g, ks->presecret_polynomial[0], elgamal_p);
1299 GNUNET_CRYPTO_mpi_print_unsigned (v_data, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
1301 GNUNET_CRYPTO_hash (v_data, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, &d->commitment);
1303 d->pubkey = ks->info[ks->local_peer_idx].paillier_public_key;
1305 d->purpose.size = htonl ((sizeof *d) - offsetof (struct GNUNET_SECRETSHARING_KeygenCommitData, purpose));
1306 d->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG1);
1307 GNUNET_assert (GNUNET_OK == GNUNET_CRYPTO_eddsa_sign (my_peer_private_key, &d->purpose, &d->signature));
1309 GNUNET_CONSENSUS_insert (ks->consensus, element, NULL, NULL);
1311 gcry_mpi_release (v);
1312 GNUNET_free (element);
1317 * Functions with this signature are called whenever a message is
1320 * @param cls closure
1321 * @param client identification of the client
1322 * @param message the actual message
1324 static void handle_client_keygen (void *cls,
1325 struct GNUNET_SERVER_Client *client,
1326 const struct GNUNET_MessageHeader
1329 const struct GNUNET_SECRETSHARING_CreateMessage *msg =
1330 (const struct GNUNET_SECRETSHARING_CreateMessage *) message;
1331 struct KeygenSession *ks;
1334 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "client requested key generation\n");
1336 ks = GNUNET_new (struct KeygenSession);
1338 /* FIXME: check if client already has some session */
1340 GNUNET_CONTAINER_DLL_insert (keygen_sessions_head, keygen_sessions_tail, ks);
1342 ks->client = client;
1343 ks->client_mq = GNUNET_MQ_queue_for_server_client (client);
1345 ks->deadline = GNUNET_TIME_absolute_ntoh (msg->deadline);
1346 ks->threshold = ntohs (msg->threshold);
1347 ks->num_peers = ntohs (msg->num_peers);
1349 ks->peers = normalize_peers ((struct GNUNET_PeerIdentity *) &msg[1], ks->num_peers,
1350 &ks->num_peers, &ks->local_peer_idx);
1353 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "first round of consensus with %u peers\n", ks->num_peers);
1354 ks->consensus = GNUNET_CONSENSUS_create (cfg, ks->num_peers, ks->peers, &msg->session_id,
1355 GNUNET_TIME_absolute_ntoh (msg->start),
1356 GNUNET_TIME_absolute_ntoh (msg->deadline),
1357 keygen_round1_new_element, ks);
1359 ks->info = GNUNET_new_array (ks->num_peers, struct KeygenPeerInfo);
1361 for (i = 0; i < ks->num_peers; i++)
1362 ks->info[i].peer = ks->peers[i];
1364 GNUNET_CRYPTO_paillier_create (&ks->info[ks->local_peer_idx].paillier_public_key,
1365 &ks->paillier_private_key);
1367 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Generated paillier key pair\n", ks->local_peer_idx);
1369 generate_presecret_polynomial (ks);
1371 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Generated presecret polynomial\n", ks->local_peer_idx);
1373 insert_round1_element (ks);
1375 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Concluding for round 1\n", ks->local_peer_idx);
1377 GNUNET_CONSENSUS_conclude (ks->consensus,
1378 keygen_round1_conclude,
1381 GNUNET_SERVER_receive_done (client, GNUNET_OK);
1383 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Waiting for round 1 elements ...\n", ks->local_peer_idx);
1388 * Called when the partial decryption consensus concludes.
1391 decrypt_conclude (void *cls)
1393 struct DecryptSession *ds = cls;
1394 struct GNUNET_SECRETSHARING_DecryptResponseMessage *msg;
1395 struct GNUNET_MQ_Envelope *ev;
1396 gcry_mpi_t lagrange;
1401 unsigned int *indices;
1406 GNUNET_CONSENSUS_destroy (ds->consensus);
1407 ds->consensus = NULL;
1409 GNUNET_assert (0 != (lagrange = gcry_mpi_new (0)));
1410 GNUNET_assert (0 != (m = gcry_mpi_new (0)));
1411 GNUNET_assert (0 != (tmp = gcry_mpi_new (0)));
1412 GNUNET_assert (0 != (prod = gcry_mpi_new (0)));
1415 for (i = 0; i < ds->share->num_peers; i++)
1416 if (NULL != ds->info[i].partial_decryption)
1419 indices = GNUNET_malloc (num * sizeof (unsigned int));
1421 for (i = 0; i < ds->share->num_peers; i++)
1422 if (NULL != ds->info[i].partial_decryption)
1423 indices[j++] = ds->info[i].original_index;
1425 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: decrypt conclude, with %u peers\n",
1426 ds->share->my_peer, num);
1428 gcry_mpi_set_ui (prod, 1);
1429 for (i = 0; i < num; i++)
1432 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: index of %u: %u\n",
1433 ds->share->my_peer, i, indices[i]);
1434 compute_lagrange_coefficient (lagrange, indices[i], indices, num);
1436 gcry_mpi_powm (tmp, ds->info[indices[i]].partial_decryption, lagrange, elgamal_p);
1438 // product of all exponentiated partiel decryptions ...
1439 gcry_mpi_mulm (prod, prod, tmp, elgamal_p);
1442 GNUNET_CRYPTO_mpi_scan_unsigned (&c_2, ds->ciphertext.c2_bits, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1444 GNUNET_assert (0 != gcry_mpi_invm (prod, prod, elgamal_p));
1445 gcry_mpi_mulm (m, c_2, prod, elgamal_p);
1446 ev = GNUNET_MQ_msg (msg, GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_DECRYPT_DONE);
1447 GNUNET_CRYPTO_mpi_print_unsigned (&msg->plaintext, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, m);
1448 msg->success = htonl (1);
1449 GNUNET_MQ_send (ds->client_mq, ev);
1451 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "sent decrypt done to client\n");
1453 GNUNET_free (indices);
1455 gcry_mpi_release(lagrange);
1456 gcry_mpi_release(m);
1457 gcry_mpi_release(tmp);
1458 gcry_mpi_release(prod);
1459 gcry_mpi_release(c_2);
1461 // FIXME: what if not enough peers participated?
1466 * Get a string representation of an MPI.
1467 * The caller must free the returned string.
1469 * @param mpi mpi to convert to a string
1470 * @return string representation of @a mpi, must be free'd by the caller
1473 mpi_to_str (gcry_mpi_t mpi)
1477 GNUNET_assert (0 == gcry_mpi_aprint (GCRYMPI_FMT_HEX, &buf, NULL, mpi));
1478 return (char *) buf;
1483 * Called when a new partial decryption arrives.
1486 decrypt_new_element (void *cls,
1487 const struct GNUNET_SET_Element *element)
1489 struct DecryptSession *session = cls;
1490 const struct GNUNET_SECRETSHARING_DecryptData *d;
1491 struct DecryptPeerInfo *info;
1492 struct GNUNET_HashCode challenge_hash;
1496 /* nizk challenge */
1497 gcry_mpi_t challenge;
1498 /* nizk commit1, g^\beta */
1500 /* nizk commit2, c_1^\beta */
1502 /* homomorphic commitment to the peer's share,
1503 * public key share */
1505 /* partial decryption we received */
1507 /* ciphertext component #1 */
1509 /* temporary variable (for comparision) #1 */
1511 /* temporary variable (for comparision) #2 */
1514 if (NULL == element)
1516 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decryption failed\n");
1517 /* FIXME: destroy */
1521 if (element->size != sizeof *d)
1523 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "element of wrong size in decrypt consensus\n");
1529 info = get_decrypt_peer_info (session, &d->peer);
1533 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decrypt element from invalid peer (%s)\n",
1534 GNUNET_i2s (&d->peer));
1538 if (NULL != info->partial_decryption)
1540 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decrypt element duplicate\n",
1541 GNUNET_i2s (&d->peer));
1545 if (0 != memcmp (&d->ciphertext, &session->ciphertext, sizeof (struct GNUNET_SECRETSHARING_Ciphertext)))
1547 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: got decrypt element with non-matching ciphertext from P%u\n",
1548 (unsigned int) session->share->my_peer, (unsigned int) (info - session->info));
1554 GNUNET_CRYPTO_hash (offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext) + (char *) d,
1555 offsetof (struct GNUNET_SECRETSHARING_DecryptData, nizk_response) -
1556 offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext),
1559 GNUNET_CRYPTO_mpi_scan_unsigned (&challenge, &challenge_hash,
1560 sizeof (struct GNUNET_HashCode));
1562 GNUNET_CRYPTO_mpi_scan_unsigned (&sigma, &session->share->sigmas[info - session->info],
1563 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1565 GNUNET_CRYPTO_mpi_scan_unsigned (&c1, session->ciphertext.c1_bits,
1566 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1568 GNUNET_CRYPTO_mpi_scan_unsigned (&commit1, &d->nizk_commit1,
1569 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1571 GNUNET_CRYPTO_mpi_scan_unsigned (&commit2, &d->nizk_commit2,
1572 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1574 GNUNET_CRYPTO_mpi_scan_unsigned (&r, &d->nizk_response,
1575 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1577 GNUNET_CRYPTO_mpi_scan_unsigned (&w, &d->partial_decryption,
1578 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1580 GNUNET_assert (NULL != (tmp1 = gcry_mpi_new (0)));
1581 GNUNET_assert (NULL != (tmp2 = gcry_mpi_new (0)));
1584 gcry_mpi_powm (tmp1, elgamal_g, r, elgamal_p);
1586 // tmp2 = g^\beta * \sigma^challenge
1587 gcry_mpi_powm (tmp2, sigma, challenge, elgamal_p);
1588 gcry_mpi_mulm (tmp2, tmp2, commit1, elgamal_p);
1590 if (0 != gcry_mpi_cmp (tmp1, tmp2))
1594 tmp1_str = mpi_to_str (tmp1);
1595 tmp2_str = mpi_to_str (tmp2);
1596 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: Received invalid partial decryption from P%u (eqn 1), expected %s got %s\n",
1597 session->share->my_peer, info - session->info, tmp1_str, tmp2_str);
1598 GNUNET_free (tmp1_str);
1599 GNUNET_free (tmp2_str);
1604 gcry_mpi_powm (tmp1, c1, r, elgamal_p);
1606 gcry_mpi_powm (tmp2, w, challenge, elgamal_p);
1607 gcry_mpi_mulm (tmp2, tmp2, commit2, elgamal_p);
1610 if (0 != gcry_mpi_cmp (tmp1, tmp2))
1612 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: Received invalid partial decryption from P%u (eqn 2)\n",
1613 session->share->my_peer, info - session->info);
1618 GNUNET_CRYPTO_mpi_scan_unsigned (&info->partial_decryption, &d->partial_decryption,
1619 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1621 gcry_mpi_release (tmp1);
1622 gcry_mpi_release (tmp2);
1623 gcry_mpi_release (sigma);
1624 gcry_mpi_release (commit1);
1625 gcry_mpi_release (commit2);
1626 gcry_mpi_release (r);
1627 gcry_mpi_release (w);
1628 gcry_mpi_release (challenge);
1629 gcry_mpi_release (c1);
1634 insert_decrypt_element (struct DecryptSession *ds)
1636 struct GNUNET_SECRETSHARING_DecryptData d;
1637 struct GNUNET_SET_Element element;
1640 /* partial decryption with our share */
1642 /* first component of the elgamal ciphertext */
1644 /* nonce for dlog zkp */
1647 gcry_mpi_t challenge;
1649 struct GNUNET_HashCode challenge_hash;
1651 /* make vagrind happy until we implement the real deal ... */
1652 memset (&d, 0, sizeof d);
1654 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting decrypt element\n",
1655 ds->share->my_peer);
1657 GNUNET_assert (ds->share->my_peer < ds->share->num_peers);
1659 GNUNET_CRYPTO_mpi_scan_unsigned (&c1, &ds->ciphertext.c1_bits,
1660 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1661 GNUNET_CRYPTO_mpi_scan_unsigned (&s, &ds->share->my_share,
1662 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1663 GNUNET_CRYPTO_mpi_scan_unsigned (&sigma, &ds->share->sigmas[ds->share->my_peer],
1664 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1666 GNUNET_assert (NULL != (w = gcry_mpi_new (0)));
1667 GNUNET_assert (NULL != (beta = gcry_mpi_new (0)));
1668 GNUNET_assert (NULL != (tmp = gcry_mpi_new (0)));
1670 // FIXME: unnecessary, remove once crypto works
1671 gcry_mpi_powm (tmp, elgamal_g, s, elgamal_p);
1672 if (0 != gcry_mpi_cmp (tmp, sigma))
1674 char *sigma_str = mpi_to_str (sigma);
1675 char *tmp_str = mpi_to_str (tmp);
1676 char *s_str = mpi_to_str (s);
1677 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Share of P%u is invalid, ref sigma %s, "
1678 "computed sigma %s, s %s\n",
1680 sigma_str, tmp_str, s_str);
1681 GNUNET_free (sigma_str);
1682 GNUNET_free (tmp_str);
1683 GNUNET_free (s_str);
1686 gcry_mpi_powm (w, c1, s, elgamal_p);
1688 element.data = (void *) &d;
1689 element.size = sizeof (struct GNUNET_SECRETSHARING_DecryptData);
1692 d.ciphertext = ds->ciphertext;
1694 GNUNET_CRYPTO_mpi_print_unsigned (&d.partial_decryption, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, w);
1696 // create the zero knowledge proof
1697 // randomly choose beta such that 0 < beta < q
1700 gcry_mpi_randomize (beta, GNUNET_SECRETSHARING_ELGAMAL_BITS - 1, GCRY_WEAK_RANDOM);
1701 } while ((gcry_mpi_cmp_ui (beta, 0) == 0) || (gcry_mpi_cmp (beta, elgamal_q) >= 0));
1703 gcry_mpi_powm (tmp, elgamal_g, beta, elgamal_p);
1704 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_commit1, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
1706 gcry_mpi_powm (tmp, c1, beta, elgamal_p);
1707 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_commit2, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
1709 // the challenge is the hash of everything up to the response
1710 GNUNET_CRYPTO_hash (offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext) + (char *) &d,
1711 offsetof (struct GNUNET_SECRETSHARING_DecryptData, nizk_response) -
1712 offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext),
1715 GNUNET_CRYPTO_mpi_scan_unsigned (&challenge, &challenge_hash,
1716 sizeof (struct GNUNET_HashCode));
1718 // compute the response in tmp,
1719 // tmp = (c * s + beta) mod q
1720 gcry_mpi_mulm (tmp, challenge, s, elgamal_q);
1721 gcry_mpi_addm (tmp, tmp, beta, elgamal_q);
1723 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_response, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
1725 d.purpose.size = htonl (element.size - offsetof (struct GNUNET_SECRETSHARING_DecryptData, purpose));
1726 d.purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DECRYPTION);
1728 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key, &d.purpose, &d.signature);
1730 GNUNET_CONSENSUS_insert (ds->consensus, &element, NULL, NULL);
1731 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting decrypt element done!\n",
1732 ds->share->my_peer);
1734 gcry_mpi_release (s);
1735 gcry_mpi_release (w);
1736 gcry_mpi_release (c1);
1737 gcry_mpi_release (beta);
1738 gcry_mpi_release (tmp);
1739 gcry_mpi_release (challenge);
1740 gcry_mpi_release (sigma);
1745 * Functions with this signature are called whenever a message is
1748 * @param cls closure
1749 * @param client identification of the client
1750 * @param message the actual message
1752 static void handle_client_decrypt (void *cls,
1753 struct GNUNET_SERVER_Client *client,
1754 const struct GNUNET_MessageHeader
1757 const struct GNUNET_SECRETSHARING_DecryptRequestMessage *msg =
1758 (const void *) message;
1759 struct DecryptSession *ds;
1760 struct GNUNET_HashCode session_id;
1763 ds = GNUNET_new (struct DecryptSession);
1764 // FIXME: check if session already exists
1765 GNUNET_CONTAINER_DLL_insert (decrypt_sessions_head, decrypt_sessions_tail, ds);
1766 ds->client = client;
1767 ds->client_mq = GNUNET_MQ_queue_for_server_client (client);
1768 ds->start = GNUNET_TIME_absolute_ntoh (msg->start);
1769 ds->deadline = GNUNET_TIME_absolute_ntoh (msg->deadline);
1770 ds->ciphertext = msg->ciphertext;
1772 ds->share = GNUNET_SECRETSHARING_share_read (&msg[1], ntohs (msg->header.size) - sizeof *msg, NULL);
1773 // FIXME: probably should be break rather than assert
1774 GNUNET_assert (NULL != ds->share);
1776 // FIXME: this is probably sufficient, but kdf/hash with all values would be nicer ...
1777 GNUNET_CRYPTO_hash (&msg->ciphertext, sizeof (struct GNUNET_SECRETSHARING_Ciphertext), &session_id);
1779 ds->consensus = GNUNET_CONSENSUS_create (cfg,
1780 ds->share->num_peers,
1785 &decrypt_new_element,
1789 ds->info = GNUNET_new_array (ds->share->num_peers, struct DecryptPeerInfo);
1790 for (i = 0; i < ds->share->num_peers; i++)
1792 ds->info[i].peer = ds->share->peers[i];
1793 ds->info[i].original_index = ds->share->original_indices[i];
1796 insert_decrypt_element (ds);
1798 GNUNET_CONSENSUS_conclude (ds->consensus, decrypt_conclude, ds);
1800 GNUNET_SERVER_receive_done (client, GNUNET_OK);
1802 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "decrypting with %u peers\n",
1803 ds->share->num_peers);
1808 init_crypto_constants (void)
1810 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_q, GCRYMPI_FMT_HEX,
1811 GNUNET_SECRETSHARING_ELGAMAL_Q_HEX, 0, NULL));
1812 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_p, GCRYMPI_FMT_HEX,
1813 GNUNET_SECRETSHARING_ELGAMAL_P_HEX, 0, NULL));
1814 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_g, GCRYMPI_FMT_HEX,
1815 GNUNET_SECRETSHARING_ELGAMAL_G_HEX, 0, NULL));
1819 static struct KeygenSession *
1820 keygen_session_get (struct GNUNET_SERVER_Client *client)
1822 struct KeygenSession *ks;
1823 for (ks = keygen_sessions_head; NULL != ks; ks = ks->next)
1824 if (ks->client == client)
1829 static struct DecryptSession *
1830 decrypt_session_get (struct GNUNET_SERVER_Client *client)
1832 struct DecryptSession *ds;
1833 for (ds = decrypt_sessions_head; NULL != ds; ds = ds->next)
1834 if (ds->client == client)
1841 * Clean up after a client has disconnected
1843 * @param cls closure, unused
1844 * @param client the client to clean up after
1847 handle_client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
1849 struct KeygenSession *ks;
1850 struct DecryptSession *ds;
1852 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "handling client disconnect\n");
1854 ks = keygen_session_get (client);
1856 keygen_session_destroy (ks);
1858 ds = decrypt_session_get (client);
1860 decrypt_session_destroy (ds);
1865 * Process template requests.
1867 * @param cls closure
1868 * @param server the initialized server
1869 * @param c configuration to use
1872 run (void *cls, struct GNUNET_SERVER_Handle *server,
1873 const struct GNUNET_CONFIGURATION_Handle *c)
1875 static const struct GNUNET_SERVER_MessageHandler handlers[] = {
1876 {handle_client_keygen, NULL, GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_GENERATE, 0},
1877 {handle_client_decrypt, NULL, GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_DECRYPT, 0},
1882 my_peer_private_key = GNUNET_CRYPTO_eddsa_key_create_from_configuration (c);
1883 if (NULL == my_peer_private_key)
1885 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "could not access host private key\n");
1887 GNUNET_SCHEDULER_shutdown ();
1890 init_crypto_constants ();
1891 if (GNUNET_OK != GNUNET_CRYPTO_get_peer_identity (cfg, &my_peer))
1893 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "could not retrieve host identity\n");
1895 GNUNET_SCHEDULER_shutdown ();
1898 GNUNET_SERVER_add_handlers (server, handlers);
1899 GNUNET_SERVER_disconnect_notify (server, &handle_client_disconnect, NULL);
1900 GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL, &cleanup_task,
1906 * The main function for the template service.
1908 * @param argc number of arguments from the command line
1909 * @param argv command line arguments
1910 * @return 0 ok, 1 on error
1913 main (int argc, char *const *argv)
1915 return (GNUNET_OK ==
1916 GNUNET_SERVICE_run (argc, argv, "secretsharing",
1917 GNUNET_SERVICE_OPTION_NONE, &run, NULL)) ? 0 : 1;