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->client_mq)
563 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "destroying decrypt MQ\n");
564 GNUNET_MQ_destroy (ds->client_mq);
565 ds->client_mq = NULL;
568 if (NULL != ds->client)
570 GNUNET_SERVER_client_disconnect (ds->client);
578 keygen_info_destroy (struct KeygenPeerInfo *info)
580 if (NULL != info->sigma)
582 gcry_mpi_release (info->sigma);
585 if (NULL != info->presecret_commitment)
587 gcry_mpi_release (info->presecret_commitment);
588 info->presecret_commitment = NULL;
590 if (NULL != info->preshare_commitment)
592 gcry_mpi_release (info->preshare_commitment);
593 info->presecret_commitment = NULL;
599 keygen_session_destroy (struct KeygenSession *ks)
601 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "destroying keygen session\n");
603 GNUNET_CONTAINER_DLL_remove (keygen_sessions_head, keygen_sessions_tail, ks);
605 if (NULL != ks->info)
608 for (i = 0; i < ks->num_peers; i++)
609 keygen_info_destroy (&ks->info[i]);
610 GNUNET_free (ks->info);
614 if (NULL != ks->consensus)
616 GNUNET_CONSENSUS_destroy (ks->consensus);
617 ks->consensus = NULL;
620 if (NULL != ks->presecret_polynomial)
623 for (i = 0; i < ks->threshold; i++)
625 GNUNET_assert (NULL != ks->presecret_polynomial[i]);
626 gcry_mpi_release (ks->presecret_polynomial[i]);
627 ks->presecret_polynomial[i] = NULL;
629 GNUNET_free (ks->presecret_polynomial);
630 ks->presecret_polynomial = NULL;
633 if (NULL != ks->client_mq)
635 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "destroying keygen MQ\n");
636 GNUNET_MQ_destroy (ks->client_mq);
637 ks->client_mq = NULL;
640 if (NULL != ks->my_share)
642 gcry_mpi_release (ks->my_share);
646 if (NULL != ks->public_key)
648 gcry_mpi_release (ks->public_key);
649 ks->public_key = NULL;
652 if (NULL != ks->peers)
654 GNUNET_free (ks->peers);
658 if (NULL != ks->client)
660 GNUNET_SERVER_client_disconnect (ks->client);
669 * Task run during shutdown.
675 cleanup_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
677 while (NULL != decrypt_sessions_head)
678 decrypt_session_destroy (decrypt_sessions_head);
680 while (NULL != keygen_sessions_head)
681 keygen_session_destroy (keygen_sessions_head);
687 * Generate the random coefficients of our pre-secret polynomial
689 * @param ks the session
692 generate_presecret_polynomial (struct KeygenSession *ks)
697 GNUNET_assert (NULL == ks->presecret_polynomial);
698 ks->presecret_polynomial = GNUNET_new_array (ks->threshold, gcry_mpi_t);
699 for (i = 0; i < ks->threshold; i++)
701 v = ks->presecret_polynomial[i] = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS);
702 GNUNET_assert (NULL != v);
703 // Randomize v such that 0 < v < elgamal_q.
704 // The '- 1' is necessary as bitlength(q) = bitlength(p) - 1.
707 gcry_mpi_randomize (v, GNUNET_SECRETSHARING_ELGAMAL_BITS - 1, GCRY_WEAK_RANDOM);
708 } while ((gcry_mpi_cmp_ui (v, 0) == 0) || (gcry_mpi_cmp (v, elgamal_q) >= 0));
714 * Consensus element handler for round one.
715 * We should get one ephemeral key for each peer.
717 * @param cls Closure (keygen session).
718 * @param element The element from consensus, or
719 * NULL if consensus failed.
722 keygen_round1_new_element (void *cls,
723 const struct GNUNET_SET_Element *element)
725 const struct GNUNET_SECRETSHARING_KeygenCommitData *d;
726 struct KeygenSession *ks = cls;
727 struct KeygenPeerInfo *info;
731 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "round1 consensus failed\n");
735 /* elements have fixed size */
736 if (element->size != sizeof (struct GNUNET_SECRETSHARING_KeygenCommitData))
738 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
739 "keygen commit data with wrong size (%u) in consensus, "
741 element->size, sizeof (struct GNUNET_SECRETSHARING_KeygenCommitData));
745 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "got round1 element\n");
748 info = get_keygen_peer_info (ks, &d->peer);
752 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong peer identity (%s) in consensus\n",
753 GNUNET_i2s (&d->peer));
757 /* Check that the right amount of data has been signed. */
758 if (d->purpose.size !=
759 htonl (element->size - offsetof (struct GNUNET_SECRETSHARING_KeygenCommitData, purpose)))
761 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong signature purpose size in consensus\n");
765 if (GNUNET_OK != GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG1,
766 &d->purpose, &d->signature, &d->peer.public_key))
768 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with invalid signature in consensus\n");
771 info->paillier_public_key = d->pubkey;
772 GNUNET_CRYPTO_mpi_scan_unsigned (&info->presecret_commitment, &d->commitment, 512 / 8);
773 info->round1_valid = GNUNET_YES;
778 * Evaluate the polynomial with coefficients @a coeff at @a x.
779 * The i-th element in @a coeff corresponds to the coefficient of x^i.
781 * @param[out] z result of the evaluation
782 * @param coeff array of coefficients
783 * @param num_coeff number of coefficients
784 * @param x where to evaluate the polynomial
785 * @param m what group are we operating in?
788 horner_eval (gcry_mpi_t z, gcry_mpi_t *coeff, unsigned int num_coeff, gcry_mpi_t x, gcry_mpi_t m)
792 gcry_mpi_set_ui (z, 0);
793 for (i = 0; i < num_coeff; i++)
796 gcry_mpi_mul (z, z, x);
797 gcry_mpi_addm (z, z, coeff[num_coeff - i - 1], m);
803 keygen_round2_conclude (void *cls)
805 struct KeygenSession *ks = cls;
806 struct GNUNET_SECRETSHARING_SecretReadyMessage *m;
807 struct GNUNET_MQ_Envelope *ev;
811 struct GNUNET_SECRETSHARING_Share *share;
813 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "round2 conclude\n");
815 GNUNET_CONSENSUS_destroy (ks->consensus);
816 ks->consensus = NULL;
818 share = GNUNET_new (struct GNUNET_SECRETSHARING_Share);
820 share->num_peers = 0;
822 for (i = 0; i < ks->num_peers; i++)
823 if (GNUNET_YES == ks->info[i].round2_valid)
826 share->peers = GNUNET_new_array (share->num_peers, struct GNUNET_PeerIdentity);
828 GNUNET_new_array (share->num_peers, struct GNUNET_SECRETSHARING_FieldElement);
829 share->original_indices = GNUNET_new_array (share->num_peers, uint16_t);
831 /* maybe we're not even in the list of peers? */
832 share->my_peer = share->num_peers;
834 j = 0; /* running index of valid peers */
835 for (i = 0; i < ks->num_peers; i++)
837 if (GNUNET_YES == ks->info[i].round2_valid)
839 share->peers[j] = ks->info[i].peer;
840 GNUNET_CRYPTO_mpi_print_unsigned (&share->sigmas[j],
841 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
843 share->original_indices[i] = j;
844 if (0 == memcmp (&share->peers[i], &my_peer, sizeof (struct GNUNET_PeerIdentity)))
850 if (share->my_peer == share->num_peers)
852 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: peer identity not in share\n", ks->local_peer_idx);
855 GNUNET_CRYPTO_mpi_print_unsigned (&share->my_share, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
857 GNUNET_CRYPTO_mpi_print_unsigned (&share->public_key, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
860 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "keygen completed with %u peers\n", share->num_peers);
862 /* Write the share. If 0 peers completed the dkg, an empty
863 * share will be sent. */
865 GNUNET_assert (GNUNET_OK == GNUNET_SECRETSHARING_share_write (share, NULL, 0, &share_size));
867 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "writing share of size %u\n",
868 (unsigned int) share_size);
870 ev = GNUNET_MQ_msg_extra (m, share_size,
871 GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_SECRET_READY);
873 GNUNET_assert (GNUNET_OK == GNUNET_SECRETSHARING_share_write (share, &m[1], share_size, NULL));
875 GNUNET_SECRETSHARING_share_destroy (share);
878 GNUNET_MQ_send (ks->client_mq, ev);
883 * Insert round 2 element in the consensus, consisting of
884 * (1) The exponentiated pre-share polynomial coefficients A_{i,l}=g^{a_{i,l}}
885 * (2) The exponentiated pre-shares y_{i,j}=g^{s_{i,j}}
886 * (3) The encrypted pre-shares Y_{i,j}
887 * (4) The zero knowledge proof for fairness of
890 * @param ks session to use
893 insert_round2_element (struct KeygenSession *ks)
895 struct GNUNET_SET_Element *element;
896 struct GNUNET_SECRETSHARING_KeygenRevealData *d;
898 unsigned char *last_pos;
904 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting round2 element\n",
907 GNUNET_assert (NULL != (v = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
908 GNUNET_assert (NULL != (idx = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
910 element_size = (sizeof (struct GNUNET_SECRETSHARING_KeygenRevealData) +
911 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->num_peers +
912 sizeof (struct GNUNET_CRYPTO_PaillierCiphertext) * ks->num_peers +
913 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->threshold);
915 element = GNUNET_malloc (sizeof (struct GNUNET_SET_Element) + element_size);
916 element->size = element_size;
917 element->data = (void *) &element[1];
919 d = (void *) element->data;
922 // start inserting vector elements
923 // after the fixed part of the element's data
924 pos = (void *) &d[1];
925 last_pos = pos + element_size;
927 // exponentiated pre-shares
928 for (i = 0; i < ks->num_peers; i++)
930 ptrdiff_t remaining = last_pos - pos;
931 GNUNET_assert (remaining > 0);
932 gcry_mpi_set_ui (idx, i + 1);
933 // evaluate the polynomial
934 horner_eval (v, ks->presecret_polynomial, ks->threshold, idx, elgamal_q);
935 // take g to the result
936 gcry_mpi_powm (v, elgamal_g, v, elgamal_p);
937 GNUNET_CRYPTO_mpi_print_unsigned (pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
938 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8;
941 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed exp preshares\n",
944 // encrypted pre-shares
945 for (i = 0; i < ks->num_peers; i++)
947 ptrdiff_t remaining = last_pos - pos;
948 struct GNUNET_CRYPTO_PaillierCiphertext *ciphertext;
950 GNUNET_assert (remaining > 0);
951 ciphertext = (void *) pos;
952 memset (ciphertext, 0, sizeof *ciphertext);
953 if (GNUNET_YES == ks->info[i].round1_valid)
955 gcry_mpi_set_ui (idx, i + 1);
956 // evaluate the polynomial
957 horner_eval (v, ks->presecret_polynomial, ks->threshold, idx, elgamal_q);
958 // encrypt the result
959 GNUNET_CRYPTO_paillier_encrypt (&ks->info[i].paillier_public_key, v, 0, ciphertext);
961 pos += sizeof *ciphertext;
964 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed enc preshares\n",
967 // exponentiated coefficients
968 for (i = 0; i < ks->threshold; i++)
970 ptrdiff_t remaining = last_pos - pos;
971 GNUNET_assert (remaining > 0);
972 gcry_mpi_powm (v, elgamal_g, ks->presecret_polynomial[i], elgamal_p);
973 GNUNET_CRYPTO_mpi_print_unsigned (pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
974 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8;
977 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed exp coefficients\n",
980 d->purpose.size = htonl (element_size - offsetof (struct GNUNET_SECRETSHARING_KeygenRevealData, purpose));
981 d->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG2);
982 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key, &d->purpose, &d->signature);
984 GNUNET_CONSENSUS_insert (ks->consensus, element, NULL, NULL);
985 GNUNET_free (element); /* FIXME: maybe stack-allocate instead? */
987 gcry_mpi_release (v);
988 gcry_mpi_release (idx);
993 keygen_reveal_get_exp_preshare (struct KeygenSession *ks,
994 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
998 gcry_mpi_t exp_preshare;
1000 GNUNET_assert (idx < ks->num_peers);
1002 pos = (void *) &d[1];
1003 // skip exponentiated pre-shares we don't want
1004 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * idx;
1005 GNUNET_CRYPTO_mpi_scan_unsigned (&exp_preshare, pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1006 return exp_preshare;
1010 keygen_reveal_get_exp_coeff (struct KeygenSession *ks,
1011 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1015 gcry_mpi_t exp_coeff;
1017 GNUNET_assert (idx < ks->threshold);
1019 pos = (void *) &d[1];
1020 // skip exponentiated pre-shares
1021 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->num_peers;
1022 // skip encrypted pre-shares
1023 pos += sizeof (struct GNUNET_CRYPTO_PaillierCiphertext) * ks->num_peers;
1024 // skip exp. coeffs we are not interested in
1025 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * idx;
1026 // the first exponentiated coefficient is the public key share
1027 GNUNET_CRYPTO_mpi_scan_unsigned (&exp_coeff, pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1032 static struct GNUNET_CRYPTO_PaillierCiphertext *
1033 keygen_reveal_get_enc_preshare (struct KeygenSession *ks,
1034 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1039 GNUNET_assert (idx < ks->num_peers);
1041 pos = (void *) &d[1];
1042 // skip exponentiated pre-shares
1043 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->num_peers;
1044 // skip encrypted pre-shares we're not interested in
1045 pos += sizeof (struct GNUNET_CRYPTO_PaillierCiphertext) * idx;
1046 return (struct GNUNET_CRYPTO_PaillierCiphertext *) pos;
1051 keygen_round2_new_element (void *cls,
1052 const struct GNUNET_SET_Element *element)
1054 struct KeygenSession *ks = cls;
1055 const struct GNUNET_SECRETSHARING_KeygenRevealData *d;
1056 struct KeygenPeerInfo *info;
1057 size_t expected_element_size;
1061 gcry_mpi_t public_key_share;
1062 gcry_mpi_t preshare;
1064 if (NULL == element)
1066 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "round2 consensus failed\n");
1070 expected_element_size = (sizeof (struct GNUNET_SECRETSHARING_KeygenRevealData) +
1071 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->num_peers +
1072 sizeof (struct GNUNET_CRYPTO_PaillierCiphertext) * ks->num_peers +
1073 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->threshold);
1075 if (element->size != expected_element_size)
1077 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1078 "keygen round2 data with wrong size (%u) in consensus, "
1080 element->size, expected_element_size);
1084 d = (const void *) element->data;
1086 info = get_keygen_peer_info (ks, &d->peer);
1090 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong peer identity (%s) in consensus\n",
1091 GNUNET_i2s (&d->peer));
1095 if (GNUNET_NO == info->round1_valid)
1097 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1098 "ignoring round2 element from peer with invalid round1 element (%s)\n",
1099 GNUNET_i2s (&d->peer));
1103 if (GNUNET_YES == info->round2_valid)
1105 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1106 "ignoring duplicate round2 element (%s)\n",
1107 GNUNET_i2s (&d->peer));
1111 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "got round2 element\n");
1113 if (ntohl (d->purpose.size) !=
1114 element->size - offsetof (struct GNUNET_SECRETSHARING_KeygenRevealData, purpose))
1116 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen reveal data with wrong signature purpose size in consensus\n");
1120 if (GNUNET_OK != GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG2,
1121 &d->purpose, &d->signature, &d->peer.public_key))
1123 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen reveal data with invalid signature in consensus\n");
1127 public_key_share = keygen_reveal_get_exp_coeff (ks, d, 0);
1128 info->preshare_commitment = keygen_reveal_get_exp_preshare (ks, d, ks->local_peer_idx);
1130 if (NULL == ks->public_key)
1132 GNUNET_assert (NULL != (ks->public_key = gcry_mpi_new (0)));
1133 gcry_mpi_set_ui (ks->public_key, 1);
1135 gcry_mpi_mulm (ks->public_key, ks->public_key, public_key_share, elgamal_p);
1137 gcry_mpi_release (public_key_share);
1138 public_key_share = NULL;
1140 GNUNET_assert (NULL != (preshare = gcry_mpi_new (0)));
1141 GNUNET_CRYPTO_paillier_decrypt (&ks->paillier_private_key,
1142 &ks->info[ks->local_peer_idx].paillier_public_key,
1143 keygen_reveal_get_enc_preshare (ks, d, ks->local_peer_idx),
1146 GNUNET_assert (NULL != (tmp = gcry_mpi_new (0)));
1147 gcry_mpi_powm (tmp, elgamal_g, preshare, elgamal_p);
1149 // TODO: restore a valid secret from the decryption (the hard part, solving SVP with gauss)
1150 cmp_result = gcry_mpi_cmp (tmp, info->preshare_commitment);
1151 gcry_mpi_release (tmp);
1153 if (0 != cmp_result)
1155 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: Got invalid presecret from P%u\n",
1156 (unsigned int) ks->local_peer_idx, (unsigned int) (info - ks->info));
1160 if (NULL == ks->my_share)
1162 GNUNET_assert (NULL != (ks->my_share = gcry_mpi_new (0)));
1164 gcry_mpi_addm (ks->my_share, ks->my_share, preshare, elgamal_q);
1166 for (j = 0; j < ks->num_peers; j++)
1168 gcry_mpi_t presigma;
1169 if (NULL == ks->info[j].sigma)
1171 GNUNET_assert (NULL != (ks->info[j].sigma = gcry_mpi_new (0)));
1172 gcry_mpi_set_ui (ks->info[j].sigma, 1);
1174 presigma = keygen_reveal_get_exp_preshare (ks, d, j);
1175 gcry_mpi_mulm (ks->info[j].sigma, ks->info[j].sigma, presigma, elgamal_p);
1176 gcry_mpi_release (presigma);
1180 GNUNET_assert (NULL != (prod = gcry_mpi_new (0)));
1182 GNUNET_assert (NULL != (j_to_k = gcry_mpi_new (0)));
1183 // validate that the polynomial sharing matches the additive sharing
1184 for (j = 0; j < ks->num_peers; j++)
1188 gcry_mpi_t exp_preshare;
1189 gcry_mpi_set_ui (prod, 1);
1190 for (k = 0; k < ks->threshold; k++)
1192 // Using pow(double,double) is a bit sketchy.
1193 // We count players from 1, but shares from 0.
1195 gcry_mpi_set_ui (j_to_k, (unsigned int) pow(j+1, k));
1196 tmp = keygen_reveal_get_exp_coeff (ks, d, k);
1197 gcry_mpi_powm (tmp, tmp, j_to_k, elgamal_p);
1198 gcry_mpi_mulm (prod, prod, tmp, elgamal_p);
1199 gcry_mpi_release (tmp);
1201 exp_preshare = keygen_reveal_get_exp_preshare (ks, d, j);
1202 gcry_mpi_mod (exp_preshare, exp_preshare, elgamal_p);
1203 cmp_result = gcry_mpi_cmp (prod, exp_preshare);
1204 gcry_mpi_release (exp_preshare);
1205 exp_preshare = NULL;
1206 if (0 != cmp_result)
1208 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: reveal data from P%u incorrect\n",
1209 ks->local_peer_idx, j);
1210 /* no need for further verification, round2 stays invalid ... */
1215 // TODO: verify proof of fair encryption (once implemented)
1217 info->round2_valid = GNUNET_YES;
1219 gcry_mpi_release (preshare);
1220 gcry_mpi_release (prod);
1221 gcry_mpi_release (j_to_k);
1226 * Called when the first consensus round has concluded.
1227 * Will initiate the second round.
1229 * @param cls closure
1232 keygen_round1_conclude (void *cls)
1234 struct KeygenSession *ks = cls;
1236 GNUNET_CONSENSUS_destroy (ks->consensus);
1238 ks->consensus = GNUNET_CONSENSUS_create (cfg, ks->num_peers, ks->peers, &ks->session_id,
1239 time_between (ks->start_time, ks->deadline, 1, 2),
1241 keygen_round2_new_element, ks);
1243 insert_round2_element (ks);
1245 GNUNET_CONSENSUS_conclude (ks->consensus,
1246 keygen_round2_conclude,
1252 * Insert the ephemeral key and the presecret commitment
1253 * of this peer in the consensus of the given session.
1255 * @param ks session to use
1258 insert_round1_element (struct KeygenSession *ks)
1260 struct GNUNET_SET_Element *element;
1261 struct GNUNET_SECRETSHARING_KeygenCommitData *d;
1264 // big-endian representation of 'v'
1265 unsigned char v_data[GNUNET_SECRETSHARING_ELGAMAL_BITS / 8];
1267 element = GNUNET_malloc (sizeof *element + sizeof *d);
1268 d = (void *) &element[1];
1270 element->size = sizeof *d;
1274 GNUNET_assert (0 != (v = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
1276 gcry_mpi_powm (v, elgamal_g, ks->presecret_polynomial[0], elgamal_p);
1278 GNUNET_CRYPTO_mpi_print_unsigned (v_data, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
1280 GNUNET_CRYPTO_hash (v_data, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, &d->commitment);
1282 d->pubkey = ks->info[ks->local_peer_idx].paillier_public_key;
1284 d->purpose.size = htonl ((sizeof *d) - offsetof (struct GNUNET_SECRETSHARING_KeygenCommitData, purpose));
1285 d->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG1);
1286 GNUNET_assert (GNUNET_OK == GNUNET_CRYPTO_eddsa_sign (my_peer_private_key, &d->purpose, &d->signature));
1288 GNUNET_CONSENSUS_insert (ks->consensus, element, NULL, NULL);
1290 gcry_mpi_release (v);
1291 GNUNET_free (element);
1296 * Functions with this signature are called whenever a message is
1299 * @param cls closure
1300 * @param client identification of the client
1301 * @param message the actual message
1303 static void handle_client_keygen (void *cls,
1304 struct GNUNET_SERVER_Client *client,
1305 const struct GNUNET_MessageHeader
1308 const struct GNUNET_SECRETSHARING_CreateMessage *msg =
1309 (const struct GNUNET_SECRETSHARING_CreateMessage *) message;
1310 struct KeygenSession *ks;
1313 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "client requested key generation\n");
1315 ks = GNUNET_new (struct KeygenSession);
1317 /* FIXME: check if client already has some session */
1319 GNUNET_CONTAINER_DLL_insert (keygen_sessions_head, keygen_sessions_tail, ks);
1321 ks->client = client;
1322 ks->client_mq = GNUNET_MQ_queue_for_server_client (client);
1324 ks->deadline = GNUNET_TIME_absolute_ntoh (msg->deadline);
1325 ks->threshold = ntohs (msg->threshold);
1326 ks->num_peers = ntohs (msg->num_peers);
1328 ks->peers = normalize_peers ((struct GNUNET_PeerIdentity *) &msg[1], ks->num_peers,
1329 &ks->num_peers, &ks->local_peer_idx);
1332 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "first round of consensus with %u peers\n", ks->num_peers);
1333 ks->consensus = GNUNET_CONSENSUS_create (cfg, ks->num_peers, ks->peers, &msg->session_id,
1334 GNUNET_TIME_absolute_ntoh (msg->start),
1335 GNUNET_TIME_absolute_ntoh (msg->deadline),
1336 keygen_round1_new_element, ks);
1338 ks->info = GNUNET_new_array (ks->num_peers, struct KeygenPeerInfo);
1340 for (i = 0; i < ks->num_peers; i++)
1341 ks->info[i].peer = ks->peers[i];
1343 GNUNET_CRYPTO_paillier_create (&ks->info[ks->local_peer_idx].paillier_public_key,
1344 &ks->paillier_private_key);
1346 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Generated paillier key pair\n", ks->local_peer_idx);
1348 generate_presecret_polynomial (ks);
1350 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Generated presecret polynomial\n", ks->local_peer_idx);
1352 insert_round1_element (ks);
1354 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Concluding for round 1\n", ks->local_peer_idx);
1356 GNUNET_CONSENSUS_conclude (ks->consensus,
1357 keygen_round1_conclude,
1360 GNUNET_SERVER_receive_done (client, GNUNET_OK);
1362 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Waiting for round 1 elements ...\n", ks->local_peer_idx);
1367 * Called when the partial decryption consensus concludes.
1370 decrypt_conclude (void *cls)
1372 struct DecryptSession *ds = cls;
1373 struct GNUNET_SECRETSHARING_DecryptResponseMessage *msg;
1374 struct GNUNET_MQ_Envelope *ev;
1375 gcry_mpi_t lagrange;
1380 unsigned int *indices;
1385 GNUNET_CONSENSUS_destroy (ds->consensus);
1386 ds->consensus = NULL;
1388 GNUNET_assert (0 != (lagrange = gcry_mpi_new (0)));
1389 GNUNET_assert (0 != (m = gcry_mpi_new (0)));
1390 GNUNET_assert (0 != (tmp = gcry_mpi_new (0)));
1391 GNUNET_assert (0 != (prod = gcry_mpi_new (0)));
1394 for (i = 0; i < ds->share->num_peers; i++)
1395 if (NULL != ds->info[i].partial_decryption)
1398 indices = GNUNET_malloc (num * sizeof (unsigned int));
1400 for (i = 0; i < ds->share->num_peers; i++)
1401 if (NULL != ds->info[i].partial_decryption)
1402 indices[j++] = ds->info[i].original_index;
1404 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: decrypt conclude, with %u peers\n",
1405 ds->share->my_peer, num);
1407 gcry_mpi_set_ui (prod, 1);
1408 for (i = 0; i < num; i++)
1411 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: index of %u: %u\n",
1412 ds->share->my_peer, i, indices[i]);
1413 compute_lagrange_coefficient (lagrange, indices[i], indices, num);
1415 gcry_mpi_powm (tmp, ds->info[indices[i]].partial_decryption, lagrange, elgamal_p);
1417 // product of all exponentiated partiel decryptions ...
1418 gcry_mpi_mulm (prod, prod, tmp, elgamal_p);
1421 GNUNET_CRYPTO_mpi_scan_unsigned (&c_2, ds->ciphertext.c2_bits, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1423 GNUNET_assert (0 != gcry_mpi_invm (prod, prod, elgamal_p));
1424 gcry_mpi_mulm (m, c_2, prod, elgamal_p);
1425 ev = GNUNET_MQ_msg (msg, GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_DECRYPT_DONE);
1426 GNUNET_CRYPTO_mpi_print_unsigned (&msg->plaintext, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, m);
1427 msg->success = htonl (1);
1428 GNUNET_MQ_send (ds->client_mq, ev);
1430 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "sent decrypt done to client\n");
1432 // FIXME: what if not enough peers participated?
1437 * Get a string representation of an MPI.
1438 * The caller must free the returned string.
1440 * @param mpi mpi to convert to a string
1441 * @return string representation of @a mpi, must be free'd by the caller
1444 mpi_to_str (gcry_mpi_t mpi)
1448 GNUNET_assert (0 == gcry_mpi_aprint (GCRYMPI_FMT_HEX, &buf, NULL, mpi));
1449 return (char *) buf;
1454 * Called when a new partial decryption arrives.
1457 decrypt_new_element (void *cls,
1458 const struct GNUNET_SET_Element *element)
1460 struct DecryptSession *session = cls;
1461 const struct GNUNET_SECRETSHARING_DecryptData *d;
1462 struct DecryptPeerInfo *info;
1463 struct GNUNET_HashCode challenge_hash;
1467 /* nizk challenge */
1468 gcry_mpi_t challenge;
1469 /* nizk commit1, g^\beta */
1471 /* nizk commit2, c_1^\beta */
1473 /* homomorphic commitment to the peer's share,
1474 * public key share */
1476 /* partial decryption we received */
1478 /* ciphertext component #1 */
1480 /* temporary variable (for comparision) #1 */
1482 /* temporary variable (for comparision) #2 */
1485 if (NULL == element)
1487 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decryption failed\n");
1488 /* FIXME: destroy */
1492 if (element->size != sizeof *d)
1494 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "element of wrong size in decrypt consensus\n");
1500 info = get_decrypt_peer_info (session, &d->peer);
1504 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decrypt element from invalid peer (%s)\n",
1505 GNUNET_i2s (&d->peer));
1509 if (NULL != info->partial_decryption)
1511 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decrypt element duplicate\n",
1512 GNUNET_i2s (&d->peer));
1516 if (0 != memcmp (&d->ciphertext, &session->ciphertext, sizeof (struct GNUNET_SECRETSHARING_Ciphertext)))
1518 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: got decrypt element with non-matching ciphertext from P%u\n",
1519 (unsigned int) session->share->my_peer, (unsigned int) (info - session->info));
1525 GNUNET_CRYPTO_hash (offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext) + (char *) d,
1526 offsetof (struct GNUNET_SECRETSHARING_DecryptData, nizk_response) -
1527 offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext),
1530 GNUNET_CRYPTO_mpi_scan_unsigned (&challenge, &challenge_hash,
1531 sizeof (struct GNUNET_HashCode));
1533 GNUNET_CRYPTO_mpi_scan_unsigned (&sigma, &session->share->sigmas[info - session->info],
1534 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1536 GNUNET_CRYPTO_mpi_scan_unsigned (&c1, session->ciphertext.c1_bits,
1537 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1539 GNUNET_CRYPTO_mpi_scan_unsigned (&commit1, &d->nizk_commit1,
1540 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1542 GNUNET_CRYPTO_mpi_scan_unsigned (&commit2, &d->nizk_commit2,
1543 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1545 GNUNET_CRYPTO_mpi_scan_unsigned (&r, &d->nizk_response,
1546 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1548 GNUNET_CRYPTO_mpi_scan_unsigned (&w, &d->partial_decryption,
1549 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1551 GNUNET_assert (NULL != (tmp1 = gcry_mpi_new (0)));
1552 GNUNET_assert (NULL != (tmp2 = gcry_mpi_new (0)));
1555 gcry_mpi_powm (tmp1, elgamal_g, r, elgamal_p);
1557 // tmp2 = g^\beta * \sigma^challenge
1558 gcry_mpi_powm (tmp2, sigma, challenge, elgamal_p);
1559 gcry_mpi_mulm (tmp2, tmp2, commit1, elgamal_p);
1561 if (0 != gcry_mpi_cmp (tmp1, tmp2))
1565 tmp1_str = mpi_to_str (tmp1);
1566 tmp2_str = mpi_to_str (tmp2);
1567 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: Received invalid partial decryption from P%u (eqn 1), expected %s got %s\n",
1568 session->share->my_peer, info - session->info, tmp1_str, tmp2_str);
1569 GNUNET_free (tmp1_str);
1570 GNUNET_free (tmp2_str);
1575 gcry_mpi_powm (tmp1, c1, r, elgamal_p);
1577 gcry_mpi_powm (tmp2, w, challenge, elgamal_p);
1578 gcry_mpi_mulm (tmp2, tmp2, commit2, elgamal_p);
1581 if (0 != gcry_mpi_cmp (tmp1, tmp2))
1583 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: Received invalid partial decryption from P%u (eqn 2)\n",
1584 session->share->my_peer, info - session->info);
1589 GNUNET_CRYPTO_mpi_scan_unsigned (&info->partial_decryption, &d->partial_decryption,
1590 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1595 insert_decrypt_element (struct DecryptSession *ds)
1597 struct GNUNET_SECRETSHARING_DecryptData d;
1598 struct GNUNET_SET_Element element;
1601 /* partial decryption with our share */
1603 /* first component of the elgamal ciphertext */
1605 /* nonce for dlog zkp */
1608 gcry_mpi_t challenge;
1610 struct GNUNET_HashCode challenge_hash;
1612 /* make vagrind happy until we implement the real deal ... */
1613 memset (&d, 0, sizeof d);
1615 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting decrypt element\n",
1616 ds->share->my_peer);
1618 GNUNET_assert (ds->share->my_peer < ds->share->num_peers);
1620 GNUNET_CRYPTO_mpi_scan_unsigned (&c1, &ds->ciphertext.c1_bits,
1621 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1622 GNUNET_CRYPTO_mpi_scan_unsigned (&s, &ds->share->my_share,
1623 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1624 GNUNET_CRYPTO_mpi_scan_unsigned (&sigma, &ds->share->sigmas[ds->share->my_peer],
1625 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1627 GNUNET_assert (NULL != (w = gcry_mpi_new (0)));
1628 GNUNET_assert (NULL != (beta = gcry_mpi_new (0)));
1629 GNUNET_assert (NULL != (tmp = gcry_mpi_new (0)));
1631 // FIXME: unnecessary, remove once crypto works
1632 gcry_mpi_powm (tmp, elgamal_g, s, elgamal_p);
1633 if (0 != gcry_mpi_cmp (tmp, sigma))
1635 char *sigma_str = mpi_to_str (sigma);
1636 char *tmp_str = mpi_to_str (tmp);
1637 char *s_str = mpi_to_str (s);
1638 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Share of P%u is invalid, ref sigma %s, "
1639 "computed sigma %s, s %s\n",
1641 sigma_str, tmp_str, s_str);
1642 GNUNET_free (sigma_str);
1643 GNUNET_free (tmp_str);
1644 GNUNET_free (s_str);
1647 gcry_mpi_powm (w, c1, s, elgamal_p);
1649 element.data = (void *) &d;
1650 element.size = sizeof (struct GNUNET_SECRETSHARING_DecryptData);
1653 d.ciphertext = ds->ciphertext;
1655 GNUNET_CRYPTO_mpi_print_unsigned (&d.partial_decryption, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, w);
1657 // create the zero knowledge proof
1658 // randomly choose beta such that 0 < beta < q
1661 gcry_mpi_randomize (beta, GNUNET_SECRETSHARING_ELGAMAL_BITS - 1, GCRY_WEAK_RANDOM);
1662 } while ((gcry_mpi_cmp_ui (beta, 0) == 0) || (gcry_mpi_cmp (beta, elgamal_q) >= 0));
1664 gcry_mpi_powm (tmp, elgamal_g, beta, elgamal_p);
1665 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_commit1, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
1667 gcry_mpi_powm (tmp, c1, beta, elgamal_p);
1668 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_commit2, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
1670 // the challenge is the hash of everything up to the response
1671 GNUNET_CRYPTO_hash (offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext) + (char *) &d,
1672 offsetof (struct GNUNET_SECRETSHARING_DecryptData, nizk_response) -
1673 offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext),
1676 GNUNET_CRYPTO_mpi_scan_unsigned (&challenge, &challenge_hash,
1677 sizeof (struct GNUNET_HashCode));
1679 // compute the response in tmp,
1680 // tmp = (c * s + beta) mod q
1681 gcry_mpi_mulm (tmp, challenge, s, elgamal_q);
1682 gcry_mpi_addm (tmp, tmp, beta, elgamal_q);
1684 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_response, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
1686 d.purpose.size = htonl (element.size - offsetof (struct GNUNET_SECRETSHARING_DecryptData, purpose));
1687 d.purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DECRYPTION);
1689 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key, &d.purpose, &d.signature);
1691 GNUNET_CONSENSUS_insert (ds->consensus, &element, NULL, NULL);
1692 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting decrypt element done!\n",
1693 ds->share->my_peer);
1698 * Functions with this signature are called whenever a message is
1701 * @param cls closure
1702 * @param client identification of the client
1703 * @param message the actual message
1705 static void handle_client_decrypt (void *cls,
1706 struct GNUNET_SERVER_Client *client,
1707 const struct GNUNET_MessageHeader
1710 const struct GNUNET_SECRETSHARING_DecryptRequestMessage *msg =
1711 (const void *) message;
1712 struct DecryptSession *ds;
1713 struct GNUNET_HashCode session_id;
1716 ds = GNUNET_new (struct DecryptSession);
1717 // FIXME: check if session already exists
1718 GNUNET_CONTAINER_DLL_insert (decrypt_sessions_head, decrypt_sessions_tail, ds);
1719 ds->client = client;
1720 ds->client_mq = GNUNET_MQ_queue_for_server_client (client);
1721 ds->start = GNUNET_TIME_absolute_ntoh (msg->start);
1722 ds->deadline = GNUNET_TIME_absolute_ntoh (msg->deadline);
1723 ds->ciphertext = msg->ciphertext;
1725 ds->share = GNUNET_SECRETSHARING_share_read (&msg[1], ntohs (msg->header.size) - sizeof *msg, NULL);
1726 // FIXME: probably should be break rather than assert
1727 GNUNET_assert (NULL != ds->share);
1729 // FIXME: this is probably sufficient, but kdf/hash with all values would be nicer ...
1730 GNUNET_CRYPTO_hash (&msg->ciphertext, sizeof (struct GNUNET_SECRETSHARING_Ciphertext), &session_id);
1732 ds->consensus = GNUNET_CONSENSUS_create (cfg,
1733 ds->share->num_peers,
1738 &decrypt_new_element,
1742 ds->info = GNUNET_new_array (ds->share->num_peers, struct DecryptPeerInfo);
1743 for (i = 0; i < ds->share->num_peers; i++)
1745 ds->info[i].peer = ds->share->peers[i];
1746 ds->info[i].original_index = ds->share->original_indices[i];
1749 insert_decrypt_element (ds);
1751 GNUNET_CONSENSUS_conclude (ds->consensus, decrypt_conclude, ds);
1753 GNUNET_SERVER_receive_done (client, GNUNET_OK);
1755 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "decrypting with %u peers\n",
1756 ds->share->num_peers);
1761 init_crypto_constants (void)
1763 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_q, GCRYMPI_FMT_HEX,
1764 GNUNET_SECRETSHARING_ELGAMAL_Q_HEX, 0, NULL));
1765 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_p, GCRYMPI_FMT_HEX,
1766 GNUNET_SECRETSHARING_ELGAMAL_P_HEX, 0, NULL));
1767 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_g, GCRYMPI_FMT_HEX,
1768 GNUNET_SECRETSHARING_ELGAMAL_G_HEX, 0, NULL));
1772 static struct KeygenSession *
1773 keygen_session_get (struct GNUNET_SERVER_Client *client)
1775 struct KeygenSession *ks;
1776 for (ks = keygen_sessions_head; NULL != ks; ks = ks->next)
1777 if (ks->client == client)
1782 static struct DecryptSession *
1783 decrypt_session_get (struct GNUNET_SERVER_Client *client)
1785 struct DecryptSession *ds;
1786 for (ds = decrypt_sessions_head; NULL != ds; ds = ds->next)
1787 if (ds->client == client)
1794 * Clean up after a client has disconnected
1796 * @param cls closure, unused
1797 * @param client the client to clean up after
1800 handle_client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
1802 struct KeygenSession *ks;
1803 struct DecryptSession *ds;
1805 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "handling client disconnect\n");
1807 ks = keygen_session_get (client);
1809 keygen_session_destroy (ks);
1811 ds = decrypt_session_get (client);
1813 decrypt_session_destroy (ds);
1818 * Process template requests.
1820 * @param cls closure
1821 * @param server the initialized server
1822 * @param c configuration to use
1825 run (void *cls, struct GNUNET_SERVER_Handle *server,
1826 const struct GNUNET_CONFIGURATION_Handle *c)
1828 static const struct GNUNET_SERVER_MessageHandler handlers[] = {
1829 {handle_client_keygen, NULL, GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_GENERATE, 0},
1830 {handle_client_decrypt, NULL, GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_DECRYPT, 0},
1835 my_peer_private_key = GNUNET_CRYPTO_eddsa_key_create_from_configuration (c);
1836 if (NULL == my_peer_private_key)
1838 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "could not access host private key\n");
1840 GNUNET_SCHEDULER_shutdown ();
1843 init_crypto_constants ();
1844 if (GNUNET_OK != GNUNET_CRYPTO_get_peer_identity (cfg, &my_peer))
1846 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "could not retrieve host identity\n");
1848 GNUNET_SCHEDULER_shutdown ();
1851 GNUNET_SERVER_add_handlers (server, handlers);
1852 GNUNET_SERVER_disconnect_notify (server, &handle_client_disconnect, NULL);
1853 GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL, &cleanup_task,
1859 * The main function for the template service.
1861 * @param argc number of arguments from the command line
1862 * @param argv command line arguments
1863 * @return 0 ok, 1 on error
1866 main (int argc, char *const *argv)
1868 return (GNUNET_OK ==
1869 GNUNET_SERVICE_run (argc, argv, "secretsharing",
1870 GNUNET_SERVICE_OPTION_NONE, &run, NULL)) ? 0 : 1;