2 This file is part of GNUnet.
3 Copyright (C) 2013 GNUnet e.V.
5 GNUnet is free software: you can redistribute it and/or modify it
6 under the terms of the GNU Affero General Public License as published
7 by the Free Software Foundation, either version 3 of the License,
8 or (at your 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 Affero General Public License for more details.
15 You should have received a copy of the GNU Affero General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
18 SPDX-License-Identifier: AGPL3.0-or-later
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 its 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 * State we keep per client.
118 * Session to establish a threshold-shared secret.
124 * Current consensus, used for both DKG rounds.
126 struct GNUNET_CONSENSUS_Handle *consensus;
129 * Which client is this for?
131 struct ClientState *cs;
134 * Randomly generated coefficients of the polynomial for sharing our
135 * pre-secret, where 'preshares[0]' is our pre-secret. Contains 'threshold'
136 * elements, thus represents a polynomial of degree 'threshold-1', which can
137 * be interpolated with 'threshold' data points.
139 * The pre-secret-shares 'i=1,...,num_peers' are given by evaluating this
140 * polyomial at 'i' for share i.
142 gcry_mpi_t *presecret_polynomial;
145 * Minimum number of shares required to restore the secret.
146 * Also the number of coefficients for the polynomial representing
147 * the sharing. Obviously, the polynomial then has degree threshold-1.
149 unsigned int threshold;
152 * Total number of peers.
154 unsigned int num_peers;
157 * Index of the local peer.
159 unsigned int local_peer;
162 * Information about all participating peers.
163 * Array of size 'num_peers'.
165 struct KeygenPeerInfo *info;
168 * List of all peers involved in the secret sharing session.
170 struct GNUNET_PeerIdentity *peers;
173 * Identifier for this session.
175 struct GNUNET_HashCode session_id;
178 * Paillier private key of our peer.
180 struct GNUNET_CRYPTO_PaillierPrivateKey paillier_private_key;
183 * When would we like the key to be established?
185 struct GNUNET_TIME_Absolute deadline;
188 * When does the DKG start? Necessary to compute fractions of the
189 * operation's desired time interval.
191 struct GNUNET_TIME_Absolute start_time;
194 * Index of the local peer in the ordered list
195 * of peers in the session.
197 unsigned int local_peer_idx;
200 * Share of our peer. Once preshares from other peers are received, they
201 * will be added to 'my'share.
206 * Public key, will be updated when a round2 element arrives.
208 gcry_mpi_t public_key;
213 * Session to cooperatively decrypt a value.
215 struct DecryptSession
219 * Handle to the consensus over partial decryptions.
221 struct GNUNET_CONSENSUS_Handle *consensus;
224 * Which client is this for?
226 struct ClientState *cs;
229 * When should we start communicating for decryption?
231 struct GNUNET_TIME_Absolute start;
234 * When would we like the ciphertext to be
237 struct GNUNET_TIME_Absolute deadline;
240 * Ciphertext we want to decrypt.
242 struct GNUNET_SECRETSHARING_Ciphertext ciphertext;
245 * Share of the local peer.
246 * Containts other important information, such as
247 * the list of other peers.
249 struct GNUNET_SECRETSHARING_Share *share;
252 * State information about other peers.
254 struct DecryptPeerInfo *info;
259 * State we keep per client.
264 * Decrypt session of the client, if any.
266 struct DecryptSession *decrypt_session;
269 * Keygen session of the client, if any.
271 struct KeygenSession *keygen_session;
274 * Client this is about.
276 struct GNUNET_SERVICE_Client *client;
279 * MQ to talk to @a client.
281 struct GNUNET_MQ_Handle *mq;
287 * The ElGamal prime field order as libgcrypt mpi.
288 * Initialized in #init_crypto_constants.
290 static gcry_mpi_t elgamal_q;
293 * Modulus of the prime field used for ElGamal.
294 * Initialized in #init_crypto_constants.
296 static gcry_mpi_t elgamal_p;
299 * Generator for prime field of order 'elgamal_q'.
300 * Initialized in #init_crypto_constants.
302 static gcry_mpi_t elgamal_g;
305 * Peer that runs this service.
307 static struct GNUNET_PeerIdentity my_peer;
310 * Peer that runs this service.
312 static struct GNUNET_CRYPTO_EddsaPrivateKey *my_peer_private_key;
315 * Configuration of this service.
317 static const struct GNUNET_CONFIGURATION_Handle *cfg;
321 * Get the peer info belonging to a peer identity in a keygen session.
323 * @param ks The keygen session.
324 * @param peer The peer identity.
325 * @return The Keygen peer info, or NULL if the peer could not be found.
327 static struct KeygenPeerInfo *
328 get_keygen_peer_info (const struct KeygenSession *ks,
329 const struct GNUNET_PeerIdentity *peer)
332 for (i = 0; i < ks->num_peers; i++)
333 if (0 == memcmp (peer, &ks->info[i].peer, sizeof (struct GNUNET_PeerIdentity)))
340 * Get the peer info belonging to a peer identity in a decrypt session.
342 * @param ds The decrypt session.
343 * @param peer The peer identity.
344 * @return The decrypt peer info, or NULL if the peer could not be found.
346 static struct DecryptPeerInfo *
347 get_decrypt_peer_info (const struct DecryptSession *ds,
348 const struct GNUNET_PeerIdentity *peer)
351 for (i = 0; i < ds->share->num_peers; i++)
352 if (0 == memcmp (peer, &ds->info[i].peer, sizeof (struct GNUNET_PeerIdentity)))
359 * Interpolate between two points in time.
361 * @param start start time
362 * @param end end time
363 * @param num numerator of the scale factor
364 * @param denum denumerator of the scale factor
366 static struct GNUNET_TIME_Absolute
367 time_between (struct GNUNET_TIME_Absolute start,
368 struct GNUNET_TIME_Absolute end,
371 struct GNUNET_TIME_Absolute result;
374 GNUNET_assert (start.abs_value_us <= end.abs_value_us);
375 diff = end.abs_value_us - start.abs_value_us;
376 result.abs_value_us = start.abs_value_us + ((diff * num) / denum);
383 * Compare two peer identities. Indended to be used with qsort or bsearch.
385 * @param p1 Some peer identity.
386 * @param p2 Some peer identity.
387 * @return 1 if p1 > p2, -1 if p1 < p2 and 0 if p1 == p2.
390 peer_id_cmp (const void *p1, const void *p2)
394 sizeof (struct GNUNET_PeerIdentity));
399 * Get the index of a peer in an array of peers
401 * @param haystack Array of peers.
402 * @param n Size of @a haystack.
403 * @param needle Peer to find
404 * @return Index of @a needle in @a haystack, or -1 if peer
405 * is not in the list.
408 peer_find (const struct GNUNET_PeerIdentity *haystack, unsigned int n,
409 const struct GNUNET_PeerIdentity *needle)
413 for (i = 0; i < n; i++)
414 if (0 == memcmp (&haystack[i],
416 sizeof (struct GNUNET_PeerIdentity)))
423 * Normalize the given list of peers, by including the local peer
424 * (if it is missing) and sorting the peers by their identity.
426 * @param listed Peers in the unnormalized list.
427 * @param num_listed Peers in the un-normalized list.
428 * @param[out] num_normalized Number of peers in the normalized list.
429 * @param[out] my_peer_idx Index of the local peer in the normalized list.
430 * @return Normalized list, must be free'd by the caller.
432 static struct GNUNET_PeerIdentity *
433 normalize_peers (struct GNUNET_PeerIdentity *listed,
434 unsigned int num_listed,
435 unsigned int *num_normalized,
436 unsigned int *my_peer_idx)
438 unsigned int local_peer_in_list;
439 /* number of peers in the normalized list */
441 struct GNUNET_PeerIdentity *normalized;
443 local_peer_in_list = GNUNET_YES;
445 if (peer_find (listed, num_listed, &my_peer) < 0)
447 local_peer_in_list = GNUNET_NO;
451 normalized = GNUNET_new_array (n,
452 struct GNUNET_PeerIdentity);
454 if (GNUNET_NO == local_peer_in_list)
455 normalized[n - 1] = my_peer;
457 GNUNET_memcpy (normalized,
459 num_listed * sizeof (struct GNUNET_PeerIdentity));
462 sizeof (struct GNUNET_PeerIdentity),
465 if (NULL != my_peer_idx)
466 *my_peer_idx = peer_find (normalized, n, &my_peer);
467 if (NULL != num_normalized)
475 * Get a the j-th lagrange coefficient for a set of indices.
477 * @param[out] coeff the lagrange coefficient
478 * @param j lagrange coefficient we want to compute
479 * @param indices indices
480 * @param num number of indices in @a indices
483 compute_lagrange_coefficient (gcry_mpi_t coeff, unsigned int j,
484 unsigned int *indices,
492 /* temp value for l-j */
495 GNUNET_assert (0 != coeff);
497 GNUNET_assert (0 != (n = gcry_mpi_new (0)));
498 GNUNET_assert (0 != (d = gcry_mpi_new (0)));
499 GNUNET_assert (0 != (tmp = gcry_mpi_new (0)));
501 gcry_mpi_set_ui (n, 1);
502 gcry_mpi_set_ui (d, 1);
504 for (i = 0; i < num; i++)
506 unsigned int l = indices[i];
509 gcry_mpi_mul_ui (n, n, l + 1);
511 gcry_mpi_set_ui (tmp, l + 1);
512 gcry_mpi_sub_ui (tmp, tmp, j + 1);
513 gcry_mpi_mul (d, d, tmp);
516 // gcry_mpi_invm does not like negative numbers ...
517 gcry_mpi_mod (d, d, elgamal_q);
519 GNUNET_assert (gcry_mpi_cmp_ui (d, 0) > 0);
521 // now we do the actual division, with everything mod q, as we
522 // are not operating on elements from <g>, but on exponents
523 GNUNET_assert (0 != gcry_mpi_invm (d, d, elgamal_q));
525 gcry_mpi_mulm (coeff, n, d, elgamal_q);
527 gcry_mpi_release (n);
528 gcry_mpi_release (d);
529 gcry_mpi_release (tmp);
534 * Destroy a decrypt session, removing it from
535 * the linked list of decrypt sessions.
537 * @param ds decrypt session to destroy
540 decrypt_session_destroy (struct DecryptSession *ds)
542 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
543 "destroying decrypt session\n");
546 ds->cs->decrypt_session = NULL;
549 if (NULL != ds->consensus)
551 GNUNET_CONSENSUS_destroy (ds->consensus);
552 ds->consensus = NULL;
555 if (NULL != ds->info)
557 for (unsigned int i = 0; i < ds->share->num_peers; i++)
559 if (NULL != ds->info[i].partial_decryption)
561 gcry_mpi_release (ds->info[i].partial_decryption);
562 ds->info[i].partial_decryption = NULL;
565 GNUNET_free (ds->info);
568 if (NULL != ds->share)
570 GNUNET_SECRETSHARING_share_destroy (ds->share);
579 keygen_info_destroy (struct KeygenPeerInfo *info)
581 if (NULL != info->sigma)
583 gcry_mpi_release (info->sigma);
586 if (NULL != info->presecret_commitment)
588 gcry_mpi_release (info->presecret_commitment);
589 info->presecret_commitment = NULL;
591 if (NULL != info->preshare_commitment)
593 gcry_mpi_release (info->preshare_commitment);
594 info->preshare_commitment = NULL;
600 keygen_session_destroy (struct KeygenSession *ks)
602 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
603 "destroying keygen session\n");
607 ks->cs->keygen_session = NULL;
610 if (NULL != ks->info)
612 for (unsigned int i = 0; i < ks->num_peers; i++)
613 keygen_info_destroy (&ks->info[i]);
614 GNUNET_free (ks->info);
618 if (NULL != ks->consensus)
620 GNUNET_CONSENSUS_destroy (ks->consensus);
621 ks->consensus = NULL;
624 if (NULL != ks->presecret_polynomial)
626 for (unsigned int i = 0; i < ks->threshold; i++)
628 GNUNET_assert (NULL != ks->presecret_polynomial[i]);
629 gcry_mpi_release (ks->presecret_polynomial[i]);
630 ks->presecret_polynomial[i] = NULL;
632 GNUNET_free (ks->presecret_polynomial);
633 ks->presecret_polynomial = NULL;
635 if (NULL != ks->my_share)
637 gcry_mpi_release (ks->my_share);
640 if (NULL != ks->public_key)
642 gcry_mpi_release (ks->public_key);
643 ks->public_key = NULL;
645 if (NULL != ks->peers)
647 GNUNET_free (ks->peers);
655 * Task run during shutdown.
661 cleanup_task (void *cls)
669 * Generate the random coefficients of our pre-secret polynomial
671 * @param ks the session
674 generate_presecret_polynomial (struct KeygenSession *ks)
679 GNUNET_assert (NULL == ks->presecret_polynomial);
680 ks->presecret_polynomial = GNUNET_new_array (ks->threshold,
682 for (i = 0; i < ks->threshold; i++)
684 v = ks->presecret_polynomial[i] = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS);
685 GNUNET_assert (NULL != v);
686 // Randomize v such that 0 < v < elgamal_q.
687 // The '- 1' is necessary as bitlength(q) = bitlength(p) - 1.
690 gcry_mpi_randomize (v, GNUNET_SECRETSHARING_ELGAMAL_BITS - 1, GCRY_WEAK_RANDOM);
691 } while ((gcry_mpi_cmp_ui (v, 0) == 0) || (gcry_mpi_cmp (v, elgamal_q) >= 0));
697 * Consensus element handler for round one.
698 * We should get one ephemeral key for each peer.
700 * @param cls Closure (keygen session).
701 * @param element The element from consensus, or
702 * NULL if consensus failed.
705 keygen_round1_new_element (void *cls,
706 const struct GNUNET_SET_Element *element)
708 const struct GNUNET_SECRETSHARING_KeygenCommitData *d;
709 struct KeygenSession *ks = cls;
710 struct KeygenPeerInfo *info;
714 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "round1 consensus failed\n");
718 /* elements have fixed size */
719 if (element->size != sizeof (struct GNUNET_SECRETSHARING_KeygenCommitData))
721 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
722 "keygen commit data with wrong size (%u) in consensus, %u expected\n",
723 (unsigned int) element->size,
724 (unsigned int) sizeof (struct GNUNET_SECRETSHARING_KeygenCommitData));
728 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "got round1 element\n");
731 info = get_keygen_peer_info (ks, &d->peer);
735 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong peer identity (%s) in consensus\n",
736 GNUNET_i2s (&d->peer));
740 /* Check that the right amount of data has been signed. */
741 if (d->purpose.size !=
742 htonl (element->size - offsetof (struct GNUNET_SECRETSHARING_KeygenCommitData, purpose)))
744 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong signature purpose size in consensus\n");
748 if (GNUNET_OK != GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG1,
749 &d->purpose, &d->signature, &d->peer.public_key))
751 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with invalid signature in consensus\n");
754 info->paillier_public_key = d->pubkey;
755 GNUNET_CRYPTO_mpi_scan_unsigned (&info->presecret_commitment, &d->commitment, 512 / 8);
756 info->round1_valid = GNUNET_YES;
761 * Evaluate the polynomial with coefficients @a coeff at @a x.
762 * The i-th element in @a coeff corresponds to the coefficient of x^i.
764 * @param[out] z result of the evaluation
765 * @param coeff array of coefficients
766 * @param num_coeff number of coefficients
767 * @param x where to evaluate the polynomial
768 * @param m what group are we operating in?
771 horner_eval (gcry_mpi_t z, gcry_mpi_t *coeff, unsigned int num_coeff, gcry_mpi_t x, gcry_mpi_t m)
775 gcry_mpi_set_ui (z, 0);
776 for (i = 0; i < num_coeff; i++)
779 gcry_mpi_mul (z, z, x);
780 gcry_mpi_addm (z, z, coeff[num_coeff - i - 1], m);
786 keygen_round2_conclude (void *cls)
788 struct KeygenSession *ks = cls;
789 struct GNUNET_SECRETSHARING_SecretReadyMessage *m;
790 struct GNUNET_MQ_Envelope *ev;
794 struct GNUNET_SECRETSHARING_Share *share;
796 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "round2 conclude\n");
798 GNUNET_CONSENSUS_destroy (ks->consensus);
799 ks->consensus = NULL;
801 share = GNUNET_new (struct GNUNET_SECRETSHARING_Share);
803 share->num_peers = 0;
805 for (i = 0; i < ks->num_peers; i++)
806 if (GNUNET_YES == ks->info[i].round2_valid)
809 share->peers = GNUNET_new_array (share->num_peers,
810 struct GNUNET_PeerIdentity);
812 GNUNET_new_array (share->num_peers,
813 struct GNUNET_SECRETSHARING_FieldElement);
814 share->original_indices = GNUNET_new_array (share->num_peers,
817 /* maybe we're not even in the list of peers? */
818 share->my_peer = share->num_peers;
820 j = 0; /* running index of valid peers */
821 for (i = 0; i < ks->num_peers; i++)
823 if (GNUNET_YES == ks->info[i].round2_valid)
825 share->peers[j] = ks->info[i].peer;
826 GNUNET_CRYPTO_mpi_print_unsigned (&share->sigmas[j],
827 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
829 share->original_indices[i] = j;
830 if (0 == memcmp (&share->peers[i], &my_peer, sizeof (struct GNUNET_PeerIdentity)))
836 if (share->my_peer == share->num_peers)
838 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: peer identity not in share\n", ks->local_peer_idx);
841 GNUNET_CRYPTO_mpi_print_unsigned (&share->my_share, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
843 GNUNET_CRYPTO_mpi_print_unsigned (&share->public_key, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
846 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "keygen completed with %u peers\n", share->num_peers);
848 /* Write the share. If 0 peers completed the dkg, an empty
849 * share will be sent. */
851 GNUNET_assert (GNUNET_OK == GNUNET_SECRETSHARING_share_write (share, NULL, 0, &share_size));
853 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "writing share of size %u\n",
854 (unsigned int) share_size);
856 ev = GNUNET_MQ_msg_extra (m, share_size,
857 GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_SECRET_READY);
859 GNUNET_assert (GNUNET_OK == GNUNET_SECRETSHARING_share_write (share, &m[1], share_size, NULL));
861 GNUNET_SECRETSHARING_share_destroy (share);
864 GNUNET_MQ_send (ks->cs->mq,
871 restore_fair (const struct GNUNET_CRYPTO_PaillierPublicKey *ppub,
872 const struct GNUNET_SECRETSHARING_FairEncryption *fe,
873 gcry_mpi_t x, gcry_mpi_t xres)
890 GNUNET_assert (NULL != (n = gcry_mpi_new (0)));
891 GNUNET_assert (NULL != (t = gcry_mpi_new (0)));
892 GNUNET_assert (NULL != (t_1 = gcry_mpi_new (0)));
893 GNUNET_assert (NULL != (t_2 = gcry_mpi_new (0)));
894 GNUNET_assert (NULL != (r = gcry_mpi_new (0)));
895 GNUNET_assert (NULL != (big_t = gcry_mpi_new (0)));
896 GNUNET_assert (NULL != (v = gcry_mpi_new (0)));
897 GNUNET_assert (NULL != (big_a = gcry_mpi_new (0)));
898 GNUNET_assert (NULL != (big_b = gcry_mpi_new (0)));
901 GNUNET_CRYPTO_mpi_scan_unsigned (&a_1, ppub, sizeof (struct GNUNET_CRYPTO_PaillierPublicKey));
902 GNUNET_assert (NULL != (a_2 = gcry_mpi_new (0)));
903 gcry_mpi_set_ui (a_2, 0);
905 GNUNET_assert (NULL != (b_1 = gcry_mpi_new (0)));
906 gcry_mpi_set (b_1, x);
907 GNUNET_assert (NULL != (b_2 = gcry_mpi_new (0)));
908 gcry_mpi_set_ui (b_2, 1);
911 gcry_mpi_mul (t, a_1, a_1);
912 gcry_mpi_mul (big_a, a_2, a_2);
913 gcry_mpi_add (big_a, big_a, t);
916 gcry_mpi_mul (t, b_1, b_1);
917 gcry_mpi_mul (big_b, b_2, b_2);
918 gcry_mpi_add (big_b, big_b, t);
923 gcry_mpi_mul (t, a_1, b_1);
924 gcry_mpi_mul (n, a_2, b_2);
925 gcry_mpi_add (n, n, t);
928 gcry_mpi_div (r, NULL, n, big_b, 0);
930 // T := A - 2rn + rrB
931 gcry_mpi_mul (v, r, n);
932 gcry_mpi_mul_ui (v, v, 2);
933 gcry_mpi_sub (big_t, big_a, v);
934 gcry_mpi_mul (v, r, r);
935 gcry_mpi_mul (v, v, big_b);
936 gcry_mpi_add (big_t, big_t, v);
938 if (gcry_mpi_cmp (big_t, big_b) >= 0)
944 gcry_mpi_mul (v, r, b_1);
945 gcry_mpi_sub (t_1, a_1, v);
946 gcry_mpi_mul (v, r, b_2);
947 gcry_mpi_sub (t_2, a_2, v);
950 gcry_mpi_set (a_1, b_1);
951 gcry_mpi_set (a_2, b_2);
953 gcry_mpi_set (b_1, t_1);
954 gcry_mpi_set (b_2, t_2);
956 gcry_mpi_set (big_a, big_b);
957 gcry_mpi_set (big_b, big_t);
961 gcry_mpi_t paillier_n;
963 GNUNET_CRYPTO_mpi_scan_unsigned (&paillier_n, ppub, sizeof (struct GNUNET_CRYPTO_PaillierPublicKey));
965 gcry_mpi_set (xres, b_2);
966 gcry_mpi_invm (xres, xres, elgamal_q);
967 gcry_mpi_mulm (xres, xres, b_1, elgamal_q);
970 gcry_mpi_release (a_1);
971 gcry_mpi_release (a_2);
972 gcry_mpi_release (b_1);
973 gcry_mpi_release (b_2);
974 gcry_mpi_release (big_a);
975 gcry_mpi_release (big_b);
976 gcry_mpi_release (big_t);
977 gcry_mpi_release (n);
978 gcry_mpi_release (t_1);
979 gcry_mpi_release (t_2);
980 gcry_mpi_release (t);
981 gcry_mpi_release (r);
982 gcry_mpi_release (v);
987 get_fair_encryption_challenge (const struct GNUNET_SECRETSHARING_FairEncryption *fe,
991 struct GNUNET_CRYPTO_PaillierCiphertext c;
992 char h[GNUNET_SECRETSHARING_ELGAMAL_BITS / 8];
993 char t1[GNUNET_SECRETSHARING_ELGAMAL_BITS / 8];
994 char t2[GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8];
996 struct GNUNET_HashCode e_hash;
1000 sizeof (hash_data));
1001 GNUNET_memcpy (&hash_data.c, &fe->c, sizeof (struct GNUNET_CRYPTO_PaillierCiphertext));
1002 GNUNET_memcpy (&hash_data.h, &fe->h, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1003 GNUNET_memcpy (&hash_data.t1, &fe->t1, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1004 GNUNET_memcpy (&hash_data.t2, &fe->t2, GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8);
1005 GNUNET_CRYPTO_hash (&hash_data,
1008 /* This allocates "e" */
1009 GNUNET_CRYPTO_mpi_scan_unsigned (e,
1011 sizeof (struct GNUNET_HashCode));
1012 gcry_mpi_mod (*e, *e, elgamal_q);
1017 verify_fair (const struct GNUNET_CRYPTO_PaillierPublicKey *ppub,
1018 const struct GNUNET_SECRETSHARING_FairEncryption *fe)
1033 GNUNET_assert (NULL != (n_sq = gcry_mpi_new (0)));
1034 GNUNET_assert (NULL != (tmp1 = gcry_mpi_new (0)));
1035 GNUNET_assert (NULL != (tmp2 = gcry_mpi_new (0)));
1037 get_fair_encryption_challenge (fe,
1038 &e /* this allocates e */);
1040 GNUNET_CRYPTO_mpi_scan_unsigned (&n,
1042 sizeof (struct GNUNET_CRYPTO_PaillierPublicKey));
1043 GNUNET_CRYPTO_mpi_scan_unsigned (&t1, fe->t1, GNUNET_CRYPTO_PAILLIER_BITS / 8);
1044 GNUNET_CRYPTO_mpi_scan_unsigned (&z, fe->z, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1045 GNUNET_CRYPTO_mpi_scan_unsigned (&y, fe->h, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1046 GNUNET_CRYPTO_mpi_scan_unsigned (&w, fe->w, GNUNET_CRYPTO_PAILLIER_BITS / 8);
1047 GNUNET_CRYPTO_mpi_scan_unsigned (&big_y, fe->c.bits, GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8);
1048 GNUNET_CRYPTO_mpi_scan_unsigned (&t2, fe->t2, GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8);
1049 gcry_mpi_mul (n_sq, n, n);
1052 gcry_mpi_powm (tmp1, elgamal_g, z, elgamal_p);
1054 gcry_mpi_powm (tmp1, y, e, elgamal_p);
1055 gcry_mpi_invm (tmp1, tmp1, elgamal_p);
1056 // tmp1 = tmp1 * tmp2
1057 gcry_mpi_mulm (tmp1, tmp1, tmp2, elgamal_p);
1059 if (0 == gcry_mpi_cmp (t1, tmp1))
1061 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "fair encryption invalid (t1)\n");
1066 gcry_mpi_powm (big_y, big_y, e, n_sq);
1067 gcry_mpi_invm (big_y, big_y, n_sq);
1069 gcry_mpi_add_ui (tmp1, n, 1);
1070 gcry_mpi_powm (tmp1, tmp1, z, n_sq);
1072 gcry_mpi_powm (tmp2, w, n, n_sq);
1074 gcry_mpi_mulm (tmp1, tmp1, tmp2, n_sq);
1075 gcry_mpi_mulm (tmp1, tmp1, big_y, n_sq);
1078 if (0 == gcry_mpi_cmp (t2, tmp1))
1080 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "fair encryption invalid (t2)\n");
1089 gcry_mpi_release (n);
1090 gcry_mpi_release (n_sq);
1091 gcry_mpi_release (z);
1092 gcry_mpi_release (t1);
1093 gcry_mpi_release (t2);
1094 gcry_mpi_release (e);
1095 gcry_mpi_release (w);
1096 gcry_mpi_release (tmp1);
1097 gcry_mpi_release (tmp2);
1098 gcry_mpi_release (y);
1099 gcry_mpi_release (big_y);
1105 * Create a fair Paillier encryption of then given ciphertext.
1107 * @param v the ciphertext
1108 * @param[out] fe the fair encryption
1111 encrypt_fair (gcry_mpi_t v,
1112 const struct GNUNET_CRYPTO_PaillierPublicKey *ppub,
1113 struct GNUNET_SECRETSHARING_FairEncryption *fe)
1129 GNUNET_assert (NULL != (r = gcry_mpi_new (0)));
1130 GNUNET_assert (NULL != (s = gcry_mpi_new (0)));
1131 GNUNET_assert (NULL != (t1 = gcry_mpi_new (0)));
1132 GNUNET_assert (NULL != (t2 = gcry_mpi_new (0)));
1133 GNUNET_assert (NULL != (z = gcry_mpi_new (0)));
1134 GNUNET_assert (NULL != (w = gcry_mpi_new (0)));
1135 GNUNET_assert (NULL != (n_sq = gcry_mpi_new (0)));
1136 GNUNET_assert (NULL != (u = gcry_mpi_new (0)));
1137 GNUNET_assert (NULL != (Y = gcry_mpi_new (0)));
1138 GNUNET_assert (NULL != (G = gcry_mpi_new (0)));
1139 GNUNET_assert (NULL != (h = gcry_mpi_new (0)));
1141 GNUNET_CRYPTO_mpi_scan_unsigned (&n,
1143 sizeof (struct GNUNET_CRYPTO_PaillierPublicKey));
1144 gcry_mpi_mul (n_sq, n, n);
1145 gcry_mpi_add_ui (G, n, 1);
1148 gcry_mpi_randomize (u, GNUNET_CRYPTO_PAILLIER_BITS, GCRY_WEAK_RANDOM);
1150 while (gcry_mpi_cmp (u, n) >= 0);
1152 gcry_mpi_powm (t1, G, v, n_sq);
1153 gcry_mpi_powm (t2, u, n, n_sq);
1154 gcry_mpi_mulm (Y, t1, t2, n_sq);
1156 GNUNET_CRYPTO_mpi_print_unsigned (fe->c.bits,
1161 gcry_mpi_randomize (r, 2048, GCRY_WEAK_RANDOM);
1163 gcry_mpi_randomize (s, GNUNET_CRYPTO_PAILLIER_BITS, GCRY_WEAK_RANDOM);
1165 while (gcry_mpi_cmp (s, n) >= 0);
1168 gcry_mpi_mulm (t1, elgamal_g, r, elgamal_p);
1169 // compute t2 (use z and w as temp)
1170 gcry_mpi_powm (z, G, r, n_sq);
1171 gcry_mpi_powm (w, s, n, n_sq);
1172 gcry_mpi_mulm (t2, z, w, n_sq);
1175 gcry_mpi_powm (h, elgamal_g, v, elgamal_p);
1177 GNUNET_CRYPTO_mpi_print_unsigned (fe->h,
1178 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
1181 GNUNET_CRYPTO_mpi_print_unsigned (fe->t1,
1182 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
1185 GNUNET_CRYPTO_mpi_print_unsigned (fe->t2,
1186 GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8,
1189 get_fair_encryption_challenge (fe,
1190 &e /* This allocates "e" */);
1193 gcry_mpi_mul (z, e, v);
1194 gcry_mpi_addm (z, z, r, elgamal_q);
1196 gcry_mpi_powm (w, u, e, n);
1197 gcry_mpi_mulm (w, w, s, n);
1199 GNUNET_CRYPTO_mpi_print_unsigned (fe->z,
1200 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
1203 GNUNET_CRYPTO_mpi_print_unsigned (fe->w,
1204 GNUNET_CRYPTO_PAILLIER_BITS / 8,
1207 gcry_mpi_release (n);
1208 gcry_mpi_release (r);
1209 gcry_mpi_release (s);
1210 gcry_mpi_release (t1);
1211 gcry_mpi_release (t2);
1212 gcry_mpi_release (z);
1213 gcry_mpi_release (w);
1214 gcry_mpi_release (e);
1215 gcry_mpi_release (n_sq);
1216 gcry_mpi_release (u);
1217 gcry_mpi_release (Y);
1218 gcry_mpi_release (G);
1219 gcry_mpi_release (h);
1224 * Insert round 2 element in the consensus, consisting of
1225 * (1) The exponentiated pre-share polynomial coefficients A_{i,l}=g^{a_{i,l}}
1226 * (2) The exponentiated pre-shares y_{i,j}=g^{s_{i,j}}
1227 * (3) The encrypted pre-shares Y_{i,j}
1228 * (4) The zero knowledge proof for fairness of
1231 * @param ks session to use
1234 insert_round2_element (struct KeygenSession *ks)
1236 struct GNUNET_SET_Element *element;
1237 struct GNUNET_SECRETSHARING_KeygenRevealData *d;
1239 unsigned char *last_pos;
1240 size_t element_size;
1245 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting round2 element\n",
1246 ks->local_peer_idx);
1248 GNUNET_assert (NULL != (v = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
1249 GNUNET_assert (NULL != (idx = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
1251 element_size = (sizeof (struct GNUNET_SECRETSHARING_KeygenRevealData) +
1252 sizeof (struct GNUNET_SECRETSHARING_FairEncryption) * ks->num_peers +
1253 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->threshold);
1255 element = GNUNET_malloc (sizeof (struct GNUNET_SET_Element) + element_size);
1256 element->size = element_size;
1257 element->data = (void *) &element[1];
1259 d = (void *) element->data;
1262 // start inserting vector elements
1263 // after the fixed part of the element's data
1264 pos = (void *) &d[1];
1265 last_pos = pos + element_size;
1267 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed exp preshares\n",
1268 ks->local_peer_idx);
1270 // encrypted pre-shares
1271 // and fair encryption proof
1273 for (i = 0; i < ks->num_peers; i++)
1275 ptrdiff_t remaining = last_pos - pos;
1276 struct GNUNET_SECRETSHARING_FairEncryption *fe = (void *) pos;
1278 GNUNET_assert (remaining > 0);
1279 memset (fe, 0, sizeof *fe);
1280 if (GNUNET_YES == ks->info[i].round1_valid)
1282 gcry_mpi_set_ui (idx, i + 1);
1283 // evaluate the polynomial
1284 horner_eval (v, ks->presecret_polynomial, ks->threshold, idx, elgamal_q);
1285 // encrypt the result
1286 encrypt_fair (v, &ks->info[i].paillier_public_key, fe);
1292 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed enc preshares\n",
1293 ks->local_peer_idx);
1295 // exponentiated coefficients
1296 for (i = 0; i < ks->threshold; i++)
1298 ptrdiff_t remaining = last_pos - pos;
1299 GNUNET_assert (remaining > 0);
1300 gcry_mpi_powm (v, elgamal_g, ks->presecret_polynomial[i], elgamal_p);
1301 GNUNET_CRYPTO_mpi_print_unsigned (pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
1302 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8;
1305 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed exp coefficients\n",
1306 ks->local_peer_idx);
1309 d->purpose.size = htonl (element_size - offsetof (struct GNUNET_SECRETSHARING_KeygenRevealData, purpose));
1310 d->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG2);
1311 GNUNET_assert (GNUNET_OK ==
1312 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key,
1316 GNUNET_CONSENSUS_insert (ks->consensus, element, NULL, NULL);
1317 GNUNET_free (element); /* FIXME: maybe stack-allocate instead? */
1319 gcry_mpi_release (v);
1320 gcry_mpi_release (idx);
1325 keygen_reveal_get_exp_coeff (struct KeygenSession *ks,
1326 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1330 gcry_mpi_t exp_coeff;
1332 GNUNET_assert (idx < ks->threshold);
1334 pos = (void *) &d[1];
1335 // skip encrypted pre-shares
1336 pos += sizeof (struct GNUNET_SECRETSHARING_FairEncryption) * ks->num_peers;
1337 // skip exp. coeffs we are not interested in
1338 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * idx;
1339 // the first exponentiated coefficient is the public key share
1340 GNUNET_CRYPTO_mpi_scan_unsigned (&exp_coeff, pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1345 static struct GNUNET_SECRETSHARING_FairEncryption *
1346 keygen_reveal_get_enc_preshare (struct KeygenSession *ks,
1347 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1352 GNUNET_assert (idx < ks->num_peers);
1354 pos = (void *) &d[1];
1355 // skip encrypted pre-shares we're not interested in
1356 pos += sizeof (struct GNUNET_SECRETSHARING_FairEncryption) * idx;
1357 return (struct GNUNET_SECRETSHARING_FairEncryption *) pos;
1362 keygen_reveal_get_exp_preshare (struct KeygenSession *ks,
1363 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1366 gcry_mpi_t exp_preshare;
1367 struct GNUNET_SECRETSHARING_FairEncryption *fe;
1369 GNUNET_assert (idx < ks->num_peers);
1370 fe = keygen_reveal_get_enc_preshare (ks, d, idx);
1371 GNUNET_CRYPTO_mpi_scan_unsigned (&exp_preshare, fe->h, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1372 return exp_preshare;
1377 keygen_round2_new_element (void *cls,
1378 const struct GNUNET_SET_Element *element)
1380 struct KeygenSession *ks = cls;
1381 const struct GNUNET_SECRETSHARING_KeygenRevealData *d;
1382 struct KeygenPeerInfo *info;
1383 size_t expected_element_size;
1387 gcry_mpi_t public_key_share;
1388 gcry_mpi_t preshare;
1390 if (NULL == element)
1392 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "round2 consensus failed\n");
1396 expected_element_size = (sizeof (struct GNUNET_SECRETSHARING_KeygenRevealData) +
1397 sizeof (struct GNUNET_SECRETSHARING_FairEncryption) * ks->num_peers +
1398 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->threshold);
1400 if (element->size != expected_element_size)
1402 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1403 "keygen round2 data with wrong size (%u) in consensus, %u expected\n",
1404 (unsigned int) element->size,
1405 (unsigned int) expected_element_size);
1409 d = (const void *) element->data;
1411 info = get_keygen_peer_info (ks, &d->peer);
1415 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong peer identity (%s) in consensus\n",
1416 GNUNET_i2s (&d->peer));
1420 if (GNUNET_NO == info->round1_valid)
1422 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1423 "ignoring round2 element from peer with invalid round1 element (%s)\n",
1424 GNUNET_i2s (&d->peer));
1428 if (GNUNET_YES == info->round2_valid)
1430 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1431 "ignoring duplicate round2 element (%s)\n",
1432 GNUNET_i2s (&d->peer));
1436 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "got round2 element\n");
1438 if (ntohl (d->purpose.size) !=
1439 element->size - offsetof (struct GNUNET_SECRETSHARING_KeygenRevealData, purpose))
1441 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen reveal data with wrong signature purpose size in consensus\n");
1445 if (GNUNET_OK != GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG2,
1446 &d->purpose, &d->signature, &d->peer.public_key))
1448 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen reveal data with invalid signature in consensus\n");
1452 public_key_share = keygen_reveal_get_exp_coeff (ks, d, 0);
1453 info->preshare_commitment = keygen_reveal_get_exp_preshare (ks, d, ks->local_peer_idx);
1455 if (NULL == ks->public_key)
1457 GNUNET_assert (NULL != (ks->public_key = gcry_mpi_new (0)));
1458 gcry_mpi_set_ui (ks->public_key, 1);
1460 gcry_mpi_mulm (ks->public_key, ks->public_key, public_key_share, elgamal_p);
1462 gcry_mpi_release (public_key_share);
1463 public_key_share = NULL;
1466 struct GNUNET_SECRETSHARING_FairEncryption *fe = keygen_reveal_get_enc_preshare (ks, d, ks->local_peer_idx);
1467 GNUNET_assert (NULL != (preshare = gcry_mpi_new (0)));
1468 GNUNET_CRYPTO_paillier_decrypt (&ks->paillier_private_key,
1469 &ks->info[ks->local_peer_idx].paillier_public_key,
1473 // FIXME: not doing the restoration is less expensive
1474 restore_fair (&ks->info[ks->local_peer_idx].paillier_public_key,
1480 GNUNET_assert (NULL != (tmp = gcry_mpi_new (0)));
1481 gcry_mpi_powm (tmp, elgamal_g, preshare, elgamal_p);
1483 cmp_result = gcry_mpi_cmp (tmp, info->preshare_commitment);
1484 gcry_mpi_release (tmp);
1486 if (0 != cmp_result)
1488 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: Got invalid presecret from P%u\n",
1489 (unsigned int) ks->local_peer_idx, (unsigned int) (info - ks->info));
1493 if (NULL == ks->my_share)
1495 GNUNET_assert (NULL != (ks->my_share = gcry_mpi_new (0)));
1497 gcry_mpi_addm (ks->my_share, ks->my_share, preshare, elgamal_q);
1499 for (j = 0; j < ks->num_peers; j++)
1501 gcry_mpi_t presigma;
1502 if (NULL == ks->info[j].sigma)
1504 GNUNET_assert (NULL != (ks->info[j].sigma = gcry_mpi_new (0)));
1505 gcry_mpi_set_ui (ks->info[j].sigma, 1);
1507 presigma = keygen_reveal_get_exp_preshare (ks, d, j);
1508 gcry_mpi_mulm (ks->info[j].sigma, ks->info[j].sigma, presigma, elgamal_p);
1509 gcry_mpi_release (presigma);
1513 GNUNET_assert (NULL != (prod = gcry_mpi_new (0)));
1515 GNUNET_assert (NULL != (j_to_k = gcry_mpi_new (0)));
1516 // validate that the polynomial sharing matches the additive sharing
1517 for (j = 0; j < ks->num_peers; j++)
1521 gcry_mpi_t exp_preshare;
1522 gcry_mpi_set_ui (prod, 1);
1523 for (k = 0; k < ks->threshold; k++)
1525 // Using pow(double,double) is a bit sketchy.
1526 // We count players from 1, but shares from 0.
1528 gcry_mpi_set_ui (j_to_k, (unsigned int) pow(j+1, k));
1529 tmp = keygen_reveal_get_exp_coeff (ks, d, k);
1530 gcry_mpi_powm (tmp, tmp, j_to_k, elgamal_p);
1531 gcry_mpi_mulm (prod, prod, tmp, elgamal_p);
1532 gcry_mpi_release (tmp);
1534 exp_preshare = keygen_reveal_get_exp_preshare (ks, d, j);
1535 gcry_mpi_mod (exp_preshare, exp_preshare, elgamal_p);
1536 cmp_result = gcry_mpi_cmp (prod, exp_preshare);
1537 gcry_mpi_release (exp_preshare);
1538 exp_preshare = NULL;
1539 if (0 != cmp_result)
1541 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: reveal data from P%u incorrect\n",
1542 ks->local_peer_idx, j);
1543 /* no need for further verification, round2 stays invalid ... */
1548 // TODO: verify proof of fair encryption (once implemented)
1549 for (j = 0; j < ks->num_peers; j++)
1551 struct GNUNET_SECRETSHARING_FairEncryption *fe = keygen_reveal_get_enc_preshare (ks, d, j);
1552 if (GNUNET_YES != verify_fair (&ks->info[j].paillier_public_key, fe))
1554 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: reveal data from P%u incorrect (fair encryption)\n",
1555 ks->local_peer_idx, j);
1561 info->round2_valid = GNUNET_YES;
1563 gcry_mpi_release (preshare);
1564 gcry_mpi_release (prod);
1565 gcry_mpi_release (j_to_k);
1570 * Called when the first consensus round has concluded.
1571 * Will initiate the second round.
1573 * @param cls closure
1576 keygen_round1_conclude (void *cls)
1578 struct KeygenSession *ks = cls;
1580 GNUNET_CONSENSUS_destroy (ks->consensus);
1582 ks->consensus = GNUNET_CONSENSUS_create (cfg, ks->num_peers, ks->peers, &ks->session_id,
1583 time_between (ks->start_time, ks->deadline, 1, 2),
1585 keygen_round2_new_element, ks);
1587 insert_round2_element (ks);
1589 GNUNET_CONSENSUS_conclude (ks->consensus,
1590 keygen_round2_conclude,
1596 * Insert the ephemeral key and the presecret commitment
1597 * of this peer in the consensus of the given session.
1599 * @param ks session to use
1602 insert_round1_element (struct KeygenSession *ks)
1604 struct GNUNET_SET_Element *element;
1605 struct GNUNET_SECRETSHARING_KeygenCommitData *d;
1608 // big-endian representation of 'v'
1609 unsigned char v_data[GNUNET_SECRETSHARING_ELGAMAL_BITS / 8];
1611 element = GNUNET_malloc (sizeof *element + sizeof *d);
1612 d = (void *) &element[1];
1614 element->size = sizeof *d;
1618 GNUNET_assert (0 != (v = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
1620 gcry_mpi_powm (v, elgamal_g, ks->presecret_polynomial[0], elgamal_p);
1622 GNUNET_CRYPTO_mpi_print_unsigned (v_data, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
1624 GNUNET_CRYPTO_hash (v_data, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, &d->commitment);
1626 d->pubkey = ks->info[ks->local_peer_idx].paillier_public_key;
1628 d->purpose.size = htonl ((sizeof *d) - offsetof (struct GNUNET_SECRETSHARING_KeygenCommitData, purpose));
1629 d->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG1);
1630 GNUNET_assert (GNUNET_OK ==
1631 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key,
1635 GNUNET_CONSENSUS_insert (ks->consensus, element, NULL, NULL);
1637 gcry_mpi_release (v);
1638 GNUNET_free (element);
1643 * Check that @a msg is well-formed.
1645 * @param cls identification of the client
1646 * @param msg the actual message
1647 * @return #GNUNET_OK if @a msg is well-formed
1650 check_client_keygen (void *cls,
1651 const struct GNUNET_SECRETSHARING_CreateMessage *msg)
1653 unsigned int num_peers = ntohs (msg->num_peers);
1655 if (ntohs (msg->header.size) - sizeof (*msg) !=
1656 num_peers * sizeof (struct GNUNET_PeerIdentity))
1659 return GNUNET_SYSERR;
1666 * Functions with this signature are called whenever a message is
1669 * @param cls identification of the client
1670 * @param msg the actual message
1673 handle_client_keygen (void *cls,
1674 const struct GNUNET_SECRETSHARING_CreateMessage *msg)
1676 struct ClientState *cs = cls;
1677 struct KeygenSession *ks;
1679 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
1680 "client requested key generation\n");
1681 if (NULL != cs->keygen_session)
1684 GNUNET_SERVICE_client_drop (cs->client);
1687 ks = GNUNET_new (struct KeygenSession);
1689 cs->keygen_session = ks;
1690 ks->deadline = GNUNET_TIME_absolute_ntoh (msg->deadline);
1691 ks->threshold = ntohs (msg->threshold);
1692 ks->num_peers = ntohs (msg->num_peers);
1694 ks->peers = normalize_peers ((struct GNUNET_PeerIdentity *) &msg[1],
1697 &ks->local_peer_idx);
1700 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
1701 "first round of consensus with %u peers\n",
1703 ks->consensus = GNUNET_CONSENSUS_create (cfg,
1707 GNUNET_TIME_absolute_ntoh (msg->start),
1708 GNUNET_TIME_absolute_ntoh (msg->deadline),
1709 keygen_round1_new_element,
1712 ks->info = GNUNET_new_array (ks->num_peers,
1713 struct KeygenPeerInfo);
1715 for (unsigned int i = 0; i < ks->num_peers; i++)
1716 ks->info[i].peer = ks->peers[i];
1718 GNUNET_CRYPTO_paillier_create (&ks->info[ks->local_peer_idx].paillier_public_key,
1719 &ks->paillier_private_key);
1721 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1722 "P%u: Generated paillier key pair\n",
1723 ks->local_peer_idx);
1724 generate_presecret_polynomial (ks);
1725 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1726 "P%u: Generated presecret polynomial\n",
1727 ks->local_peer_idx);
1728 insert_round1_element (ks);
1729 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1730 "P%u: Concluding for round 1\n",
1731 ks->local_peer_idx);
1732 GNUNET_CONSENSUS_conclude (ks->consensus,
1733 keygen_round1_conclude,
1735 GNUNET_SERVICE_client_continue (cs->client);
1736 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1737 "P%u: Waiting for round 1 elements ...\n",
1738 ks->local_peer_idx);
1743 * Called when the partial decryption consensus concludes.
1746 decrypt_conclude (void *cls)
1748 struct DecryptSession *ds = cls;
1749 struct GNUNET_SECRETSHARING_DecryptResponseMessage *msg;
1750 struct GNUNET_MQ_Envelope *ev;
1751 gcry_mpi_t lagrange;
1756 unsigned int *indices;
1761 GNUNET_CONSENSUS_destroy (ds->consensus);
1762 ds->consensus = NULL;
1764 GNUNET_assert (0 != (lagrange = gcry_mpi_new (0)));
1765 GNUNET_assert (0 != (m = gcry_mpi_new (0)));
1766 GNUNET_assert (0 != (tmp = gcry_mpi_new (0)));
1767 GNUNET_assert (0 != (prod = gcry_mpi_new (0)));
1770 for (i = 0; i < ds->share->num_peers; i++)
1771 if (NULL != ds->info[i].partial_decryption)
1774 indices = GNUNET_new_array (num,
1777 for (i = 0; i < ds->share->num_peers; i++)
1778 if (NULL != ds->info[i].partial_decryption)
1779 indices[j++] = ds->info[i].original_index;
1781 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
1782 "P%u: decrypt conclude, with %u peers\n",
1786 gcry_mpi_set_ui (prod, 1);
1787 for (i = 0; i < num; i++)
1790 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
1791 "P%u: index of %u: %u\n",
1792 ds->share->my_peer, i, indices[i]);
1793 compute_lagrange_coefficient (lagrange, indices[i], indices, num);
1795 gcry_mpi_powm (tmp, ds->info[indices[i]].partial_decryption, lagrange, elgamal_p);
1797 // product of all exponentiated partiel decryptions ...
1798 gcry_mpi_mulm (prod, prod, tmp, elgamal_p);
1801 GNUNET_CRYPTO_mpi_scan_unsigned (&c_2, ds->ciphertext.c2_bits, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1803 GNUNET_assert (0 != gcry_mpi_invm (prod, prod, elgamal_p));
1804 gcry_mpi_mulm (m, c_2, prod, elgamal_p);
1805 ev = GNUNET_MQ_msg (msg, GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_DECRYPT_DONE);
1806 GNUNET_CRYPTO_mpi_print_unsigned (&msg->plaintext, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, m);
1807 msg->success = htonl (1);
1808 GNUNET_MQ_send (ds->cs->mq,
1811 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "sent decrypt done to client\n");
1813 GNUNET_free (indices);
1815 gcry_mpi_release(lagrange);
1816 gcry_mpi_release(m);
1817 gcry_mpi_release(tmp);
1818 gcry_mpi_release(prod);
1819 gcry_mpi_release(c_2);
1821 // FIXME: what if not enough peers participated?
1826 * Get a string representation of an MPI.
1827 * The caller must free the returned string.
1829 * @param mpi mpi to convert to a string
1830 * @return string representation of @a mpi, must be free'd by the caller
1833 mpi_to_str (gcry_mpi_t mpi)
1837 GNUNET_assert (0 == gcry_mpi_aprint (GCRYMPI_FMT_HEX, &buf, NULL, mpi));
1838 return (char *) buf;
1843 * Called when a new partial decryption arrives.
1846 decrypt_new_element (void *cls,
1847 const struct GNUNET_SET_Element *element)
1849 struct DecryptSession *session = cls;
1850 const struct GNUNET_SECRETSHARING_DecryptData *d;
1851 struct DecryptPeerInfo *info;
1852 struct GNUNET_HashCode challenge_hash;
1856 /* nizk challenge */
1857 gcry_mpi_t challenge;
1858 /* nizk commit1, g^\beta */
1860 /* nizk commit2, c_1^\beta */
1862 /* homomorphic commitment to the peer's share,
1863 * public key share */
1865 /* partial decryption we received */
1867 /* ciphertext component #1 */
1869 /* temporary variable (for comparision) #1 */
1871 /* temporary variable (for comparision) #2 */
1874 if (NULL == element)
1876 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decryption failed\n");
1877 /* FIXME: destroy */
1881 if (element->size != sizeof *d)
1883 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "element of wrong size in decrypt consensus\n");
1889 info = get_decrypt_peer_info (session, &d->peer);
1893 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decrypt element from invalid peer (%s)\n",
1894 GNUNET_i2s (&d->peer));
1898 if (NULL != info->partial_decryption)
1900 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decrypt element duplicate\n");
1904 if (0 != memcmp (&d->ciphertext, &session->ciphertext, sizeof (struct GNUNET_SECRETSHARING_Ciphertext)))
1906 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: got decrypt element with non-matching ciphertext from P%u\n",
1907 (unsigned int) session->share->my_peer, (unsigned int) (info - session->info));
1913 GNUNET_CRYPTO_hash (offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext) + (char *) d,
1914 offsetof (struct GNUNET_SECRETSHARING_DecryptData, nizk_response) -
1915 offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext),
1918 GNUNET_CRYPTO_mpi_scan_unsigned (&challenge, &challenge_hash,
1919 sizeof (struct GNUNET_HashCode));
1921 GNUNET_CRYPTO_mpi_scan_unsigned (&sigma, &session->share->sigmas[info - session->info],
1922 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1924 GNUNET_CRYPTO_mpi_scan_unsigned (&c1, session->ciphertext.c1_bits,
1925 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1927 GNUNET_CRYPTO_mpi_scan_unsigned (&commit1, &d->nizk_commit1,
1928 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1930 GNUNET_CRYPTO_mpi_scan_unsigned (&commit2, &d->nizk_commit2,
1931 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1933 GNUNET_CRYPTO_mpi_scan_unsigned (&r, &d->nizk_response,
1934 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1936 GNUNET_CRYPTO_mpi_scan_unsigned (&w, &d->partial_decryption,
1937 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1939 GNUNET_assert (NULL != (tmp1 = gcry_mpi_new (0)));
1940 GNUNET_assert (NULL != (tmp2 = gcry_mpi_new (0)));
1943 gcry_mpi_powm (tmp1, elgamal_g, r, elgamal_p);
1945 // tmp2 = g^\beta * \sigma^challenge
1946 gcry_mpi_powm (tmp2, sigma, challenge, elgamal_p);
1947 gcry_mpi_mulm (tmp2, tmp2, commit1, elgamal_p);
1949 if (0 != gcry_mpi_cmp (tmp1, tmp2))
1954 tmp1_str = mpi_to_str (tmp1);
1955 tmp2_str = mpi_to_str (tmp2);
1956 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1957 "P%u: Received invalid partial decryption from P%u (eqn 1), expected %s got %s\n",
1958 session->share->my_peer,
1959 (unsigned int) (info - session->info),
1962 GNUNET_free (tmp1_str);
1963 GNUNET_free (tmp2_str);
1968 gcry_mpi_powm (tmp1, c1, r, elgamal_p);
1970 gcry_mpi_powm (tmp2, w, challenge, elgamal_p);
1971 gcry_mpi_mulm (tmp2, tmp2, commit2, elgamal_p);
1974 if (0 != gcry_mpi_cmp (tmp1, tmp2))
1976 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1977 "P%u: Received invalid partial decryption from P%u (eqn 2)\n",
1978 session->share->my_peer,
1979 (unsigned int) (info - session->info));
1984 GNUNET_CRYPTO_mpi_scan_unsigned (&info->partial_decryption, &d->partial_decryption,
1985 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1987 gcry_mpi_release (tmp1);
1988 gcry_mpi_release (tmp2);
1989 gcry_mpi_release (sigma);
1990 gcry_mpi_release (commit1);
1991 gcry_mpi_release (commit2);
1992 gcry_mpi_release (r);
1993 gcry_mpi_release (w);
1994 gcry_mpi_release (challenge);
1995 gcry_mpi_release (c1);
2000 insert_decrypt_element (struct DecryptSession *ds)
2002 struct GNUNET_SECRETSHARING_DecryptData d;
2003 struct GNUNET_SET_Element element;
2006 /* partial decryption with our share */
2008 /* first component of the elgamal ciphertext */
2010 /* nonce for dlog zkp */
2013 gcry_mpi_t challenge;
2015 struct GNUNET_HashCode challenge_hash;
2017 /* make vagrind happy until we implement the real deal ... */
2018 memset (&d, 0, sizeof d);
2020 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting decrypt element\n",
2021 ds->share->my_peer);
2023 GNUNET_assert (ds->share->my_peer < ds->share->num_peers);
2025 GNUNET_CRYPTO_mpi_scan_unsigned (&c1, &ds->ciphertext.c1_bits,
2026 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
2027 GNUNET_CRYPTO_mpi_scan_unsigned (&s, &ds->share->my_share,
2028 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
2029 GNUNET_CRYPTO_mpi_scan_unsigned (&sigma, &ds->share->sigmas[ds->share->my_peer],
2030 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
2032 GNUNET_assert (NULL != (w = gcry_mpi_new (0)));
2033 GNUNET_assert (NULL != (beta = gcry_mpi_new (0)));
2034 GNUNET_assert (NULL != (tmp = gcry_mpi_new (0)));
2036 // FIXME: unnecessary, remove once crypto works
2037 gcry_mpi_powm (tmp, elgamal_g, s, elgamal_p);
2038 if (0 != gcry_mpi_cmp (tmp, sigma))
2040 char *sigma_str = mpi_to_str (sigma);
2041 char *tmp_str = mpi_to_str (tmp);
2042 char *s_str = mpi_to_str (s);
2043 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Share of P%u is invalid, ref sigma %s, "
2044 "computed sigma %s, s %s\n",
2046 sigma_str, tmp_str, s_str);
2047 GNUNET_free (sigma_str);
2048 GNUNET_free (tmp_str);
2049 GNUNET_free (s_str);
2052 gcry_mpi_powm (w, c1, s, elgamal_p);
2054 element.data = (void *) &d;
2055 element.size = sizeof (struct GNUNET_SECRETSHARING_DecryptData);
2056 element.element_type = 0;
2058 d.ciphertext = ds->ciphertext;
2060 GNUNET_CRYPTO_mpi_print_unsigned (&d.partial_decryption, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, w);
2062 // create the zero knowledge proof
2063 // randomly choose beta such that 0 < beta < q
2066 gcry_mpi_randomize (beta, GNUNET_SECRETSHARING_ELGAMAL_BITS - 1, GCRY_WEAK_RANDOM);
2067 } while ((gcry_mpi_cmp_ui (beta, 0) == 0) || (gcry_mpi_cmp (beta, elgamal_q) >= 0));
2069 gcry_mpi_powm (tmp, elgamal_g, beta, elgamal_p);
2070 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_commit1, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
2072 gcry_mpi_powm (tmp, c1, beta, elgamal_p);
2073 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_commit2, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
2075 // the challenge is the hash of everything up to the response
2076 GNUNET_CRYPTO_hash (offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext) + (char *) &d,
2077 offsetof (struct GNUNET_SECRETSHARING_DecryptData, nizk_response) -
2078 offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext),
2081 GNUNET_CRYPTO_mpi_scan_unsigned (&challenge, &challenge_hash,
2082 sizeof (struct GNUNET_HashCode));
2084 // compute the response in tmp,
2085 // tmp = (c * s + beta) mod q
2086 gcry_mpi_mulm (tmp, challenge, s, elgamal_q);
2087 gcry_mpi_addm (tmp, tmp, beta, elgamal_q);
2089 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_response, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
2091 d.purpose.size = htonl (element.size - offsetof (struct GNUNET_SECRETSHARING_DecryptData, purpose));
2092 d.purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DECRYPTION);
2094 GNUNET_assert (GNUNET_OK ==
2095 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key,
2099 GNUNET_CONSENSUS_insert (ds->consensus, &element, NULL, NULL);
2100 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
2101 "P%u: Inserting decrypt element done!\n",
2102 ds->share->my_peer);
2104 gcry_mpi_release (s);
2105 gcry_mpi_release (w);
2106 gcry_mpi_release (c1);
2107 gcry_mpi_release (beta);
2108 gcry_mpi_release (tmp);
2109 gcry_mpi_release (challenge);
2110 gcry_mpi_release (sigma);
2115 * Check that @a msg is well-formed.
2117 * @param cls identification of the client
2118 * @param msg the actual message
2119 * @return #GNUNET_OK (check deferred a bit)
2122 check_client_decrypt (void *cls,
2123 const struct GNUNET_SECRETSHARING_DecryptRequestMessage *msg)
2125 /* we check later, it's complicated */
2131 * Functions with this signature are called whenever a message is
2134 * @param cls identification of the client
2135 * @param msg the actual message
2138 handle_client_decrypt (void *cls,
2139 const struct GNUNET_SECRETSHARING_DecryptRequestMessage *msg)
2141 struct ClientState *cs = cls;
2142 struct DecryptSession *ds;
2143 struct GNUNET_HashCode session_id;
2145 if (NULL != cs->decrypt_session)
2148 GNUNET_SERVICE_client_drop (cs->client);
2151 ds = GNUNET_new (struct DecryptSession);
2152 cs->decrypt_session = ds;
2154 ds->start = GNUNET_TIME_absolute_ntoh (msg->start);
2155 ds->deadline = GNUNET_TIME_absolute_ntoh (msg->deadline);
2156 ds->ciphertext = msg->ciphertext;
2158 ds->share = GNUNET_SECRETSHARING_share_read (&msg[1],
2159 ntohs (msg->header.size) - sizeof (*msg),
2161 if (NULL == ds->share)
2164 GNUNET_SERVICE_client_drop (cs->client);
2168 /* FIXME: this is probably sufficient, but kdf/hash with all values would be nicer ... */
2169 GNUNET_CRYPTO_hash (&msg->ciphertext,
2170 sizeof (struct GNUNET_SECRETSHARING_Ciphertext),
2172 ds->consensus = GNUNET_CONSENSUS_create (cfg,
2173 ds->share->num_peers,
2178 &decrypt_new_element,
2182 ds->info = GNUNET_new_array (ds->share->num_peers,
2183 struct DecryptPeerInfo);
2184 for (unsigned int i = 0; i < ds->share->num_peers; i++)
2186 ds->info[i].peer = ds->share->peers[i];
2187 ds->info[i].original_index = ds->share->original_indices[i];
2189 insert_decrypt_element (ds);
2190 GNUNET_CONSENSUS_conclude (ds->consensus,
2193 GNUNET_SERVICE_client_continue (cs->client);
2194 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
2195 "decrypting with %u peers\n",
2196 ds->share->num_peers);
2201 init_crypto_constants (void)
2203 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_q, GCRYMPI_FMT_HEX,
2204 GNUNET_SECRETSHARING_ELGAMAL_Q_HEX, 0, NULL));
2205 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_p, GCRYMPI_FMT_HEX,
2206 GNUNET_SECRETSHARING_ELGAMAL_P_HEX, 0, NULL));
2207 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_g, GCRYMPI_FMT_HEX,
2208 GNUNET_SECRETSHARING_ELGAMAL_G_HEX, 0, NULL));
2213 * Initialize secretsharing service.
2215 * @param cls closure
2216 * @param c configuration to use
2217 * @param service the initialized service
2221 const struct GNUNET_CONFIGURATION_Handle *c,
2222 struct GNUNET_SERVICE_Handle *service)
2225 my_peer_private_key = GNUNET_CRYPTO_eddsa_key_create_from_configuration (c);
2226 if (NULL == my_peer_private_key)
2228 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
2229 "could not access host private key\n");
2231 GNUNET_SCHEDULER_shutdown ();
2234 init_crypto_constants ();
2236 GNUNET_CRYPTO_get_peer_identity (cfg,
2239 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
2240 "could not retrieve host identity\n");
2242 GNUNET_SCHEDULER_shutdown ();
2245 GNUNET_SCHEDULER_add_shutdown (&cleanup_task,
2251 * Callback called when a client connects to the service.
2253 * @param cls closure for the service
2254 * @param c the new client that connected to the service
2255 * @param mq the message queue used to send messages to the client
2259 client_connect_cb (void *cls,
2260 struct GNUNET_SERVICE_Client *c,
2261 struct GNUNET_MQ_Handle *mq)
2263 struct ClientState *cs = GNUNET_new (struct ClientState);;
2272 * Callback called when a client disconnected from the service
2274 * @param cls closure for the service
2275 * @param c the client that disconnected
2276 * @param internal_cls should be equal to @a c
2279 client_disconnect_cb (void *cls,
2280 struct GNUNET_SERVICE_Client *c,
2283 struct ClientState *cs = internal_cls;
2285 if (NULL != cs->keygen_session)
2286 keygen_session_destroy (cs->keygen_session);
2288 if (NULL != cs->decrypt_session)
2289 decrypt_session_destroy (cs->decrypt_session);
2295 * Define "main" method using service macro.
2299 GNUNET_SERVICE_OPTION_NONE,
2302 &client_disconnect_cb,
2304 GNUNET_MQ_hd_var_size (client_keygen,
2305 GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_GENERATE,
2306 struct GNUNET_SECRETSHARING_CreateMessage,
2308 GNUNET_MQ_hd_var_size (client_decrypt,
2309 GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_DECRYPT,
2310 struct GNUNET_SECRETSHARING_DecryptRequestMessage,
2312 GNUNET_MQ_handler_end ());