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.
17 * @file secretsharing/gnunet-service-secretsharing.c
18 * @brief secret sharing service
19 * @author Florian Dold
22 #include "gnunet_util_lib.h"
23 #include "gnunet_time_lib.h"
24 #include "gnunet_signatures.h"
25 #include "gnunet_consensus_service.h"
26 #include "secretsharing.h"
27 #include "secretsharing_protocol.h"
31 #define EXTRA_CHECKS 1
35 * Info about a peer in a key generation session.
40 * Peer identity of the peer.
42 struct GNUNET_PeerIdentity peer;
45 * The peer's paillier public key.
46 * Freshly generated for each keygen session.
48 struct GNUNET_CRYPTO_PaillierPublicKey paillier_public_key;
51 * The peer's commitment to his presecret.
53 gcry_mpi_t presecret_commitment;
56 * Commitment to the preshare that is
57 * intended for our peer.
59 gcry_mpi_t preshare_commitment;
62 * Sigma (exponentiated share) for this peer.
67 * Did we successfully receive the round1 element
73 * Did we successfully receive the round2 element
81 * Information about a peer in a decrypt session.
83 struct DecryptPeerInfo
86 * Identity of the peer.
88 struct GNUNET_PeerIdentity peer;
91 * Original index in the key generation round.
92 * Necessary for computing the lagrange coefficients.
94 unsigned int original_index;
97 * Set to the partial decryption of
98 * this peer, or NULL if we did not
99 * receive a partial decryption from this
100 * peer or the zero knowledge proof failed.
102 gcry_mpi_t partial_decryption;
107 * State we keep per client.
113 * Session to establish a threshold-shared secret.
119 * Current consensus, used for both DKG rounds.
121 struct GNUNET_CONSENSUS_Handle *consensus;
124 * Which client is this for?
126 struct ClientState *cs;
129 * Randomly generated coefficients of the polynomial for sharing our
130 * pre-secret, where 'preshares[0]' is our pre-secret. Contains 'threshold'
131 * elements, thus represents a polynomial of degree 'threshold-1', which can
132 * be interpolated with 'threshold' data points.
134 * The pre-secret-shares 'i=1,...,num_peers' are given by evaluating this
135 * polyomial at 'i' for share i.
137 gcry_mpi_t *presecret_polynomial;
140 * Minimum number of shares required to restore the secret.
141 * Also the number of coefficients for the polynomial representing
142 * the sharing. Obviously, the polynomial then has degree threshold-1.
144 unsigned int threshold;
147 * Total number of peers.
149 unsigned int num_peers;
152 * Index of the local peer.
154 unsigned int local_peer;
157 * Information about all participating peers.
158 * Array of size 'num_peers'.
160 struct KeygenPeerInfo *info;
163 * List of all peers involved in the secret sharing session.
165 struct GNUNET_PeerIdentity *peers;
168 * Identifier for this session.
170 struct GNUNET_HashCode session_id;
173 * Paillier private key of our peer.
175 struct GNUNET_CRYPTO_PaillierPrivateKey paillier_private_key;
178 * When would we like the key to be established?
180 struct GNUNET_TIME_Absolute deadline;
183 * When does the DKG start? Necessary to compute fractions of the
184 * operation's desired time interval.
186 struct GNUNET_TIME_Absolute start_time;
189 * Index of the local peer in the ordered list
190 * of peers in the session.
192 unsigned int local_peer_idx;
195 * Share of our peer. Once preshares from other peers are received, they
196 * will be added to 'my'share.
201 * Public key, will be updated when a round2 element arrives.
203 gcry_mpi_t public_key;
208 * Session to cooperatively decrypt a value.
210 struct DecryptSession
214 * Handle to the consensus over partial decryptions.
216 struct GNUNET_CONSENSUS_Handle *consensus;
219 * Which client is this for?
221 struct ClientState *cs;
224 * When should we start communicating for decryption?
226 struct GNUNET_TIME_Absolute start;
229 * When would we like the ciphertext to be
232 struct GNUNET_TIME_Absolute deadline;
235 * Ciphertext we want to decrypt.
237 struct GNUNET_SECRETSHARING_Ciphertext ciphertext;
240 * Share of the local peer.
241 * Containts other important information, such as
242 * the list of other peers.
244 struct GNUNET_SECRETSHARING_Share *share;
247 * State information about other peers.
249 struct DecryptPeerInfo *info;
254 * State we keep per client.
259 * Decrypt session of the client, if any.
261 struct DecryptSession *decrypt_session;
264 * Keygen session of the client, if any.
266 struct KeygenSession *keygen_session;
269 * Client this is about.
271 struct GNUNET_SERVICE_Client *client;
274 * MQ to talk to @a client.
276 struct GNUNET_MQ_Handle *mq;
282 * The ElGamal prime field order as libgcrypt mpi.
283 * Initialized in #init_crypto_constants.
285 static gcry_mpi_t elgamal_q;
288 * Modulus of the prime field used for ElGamal.
289 * Initialized in #init_crypto_constants.
291 static gcry_mpi_t elgamal_p;
294 * Generator for prime field of order 'elgamal_q'.
295 * Initialized in #init_crypto_constants.
297 static gcry_mpi_t elgamal_g;
300 * Peer that runs this service.
302 static struct GNUNET_PeerIdentity my_peer;
305 * Peer that runs this service.
307 static struct GNUNET_CRYPTO_EddsaPrivateKey *my_peer_private_key;
310 * Configuration of this service.
312 static const struct GNUNET_CONFIGURATION_Handle *cfg;
316 * Get the peer info belonging to a peer identity in a keygen session.
318 * @param ks The keygen session.
319 * @param peer The peer identity.
320 * @return The Keygen peer info, or NULL if the peer could not be found.
322 static struct KeygenPeerInfo *
323 get_keygen_peer_info (const struct KeygenSession *ks,
324 const struct GNUNET_PeerIdentity *peer)
327 for (i = 0; i < ks->num_peers; i++)
328 if (0 == memcmp (peer, &ks->info[i].peer, sizeof (struct GNUNET_PeerIdentity)))
335 * Get the peer info belonging to a peer identity in a decrypt session.
337 * @param ds The decrypt session.
338 * @param peer The peer identity.
339 * @return The decrypt peer info, or NULL if the peer could not be found.
341 static struct DecryptPeerInfo *
342 get_decrypt_peer_info (const struct DecryptSession *ds,
343 const struct GNUNET_PeerIdentity *peer)
346 for (i = 0; i < ds->share->num_peers; i++)
347 if (0 == memcmp (peer, &ds->info[i].peer, sizeof (struct GNUNET_PeerIdentity)))
354 * Interpolate between two points in time.
356 * @param start start time
357 * @param end end time
358 * @param num numerator of the scale factor
359 * @param denum denumerator of the scale factor
361 static struct GNUNET_TIME_Absolute
362 time_between (struct GNUNET_TIME_Absolute start,
363 struct GNUNET_TIME_Absolute end,
366 struct GNUNET_TIME_Absolute result;
369 GNUNET_assert (start.abs_value_us <= end.abs_value_us);
370 diff = end.abs_value_us - start.abs_value_us;
371 result.abs_value_us = start.abs_value_us + ((diff * num) / denum);
378 * Compare two peer identities. Indended to be used with qsort or bsearch.
380 * @param p1 Some peer identity.
381 * @param p2 Some peer identity.
382 * @return 1 if p1 > p2, -1 if p1 < p2 and 0 if p1 == p2.
385 peer_id_cmp (const void *p1, const void *p2)
389 sizeof (struct GNUNET_PeerIdentity));
394 * Get the index of a peer in an array of peers
396 * @param haystack Array of peers.
397 * @param n Size of @a haystack.
398 * @param needle Peer to find
399 * @return Index of @a needle in @a haystack, or -1 if peer
400 * is not in the list.
403 peer_find (const struct GNUNET_PeerIdentity *haystack, unsigned int n,
404 const struct GNUNET_PeerIdentity *needle)
408 for (i = 0; i < n; i++)
409 if (0 == memcmp (&haystack[i],
411 sizeof (struct GNUNET_PeerIdentity)))
418 * Normalize the given list of peers, by including the local peer
419 * (if it is missing) and sorting the peers by their identity.
421 * @param listed Peers in the unnormalized list.
422 * @param num_listed Peers in the un-normalized list.
423 * @param[out] num_normalized Number of peers in the normalized list.
424 * @param[out] my_peer_idx Index of the local peer in the normalized list.
425 * @return Normalized list, must be free'd by the caller.
427 static struct GNUNET_PeerIdentity *
428 normalize_peers (struct GNUNET_PeerIdentity *listed,
429 unsigned int num_listed,
430 unsigned int *num_normalized,
431 unsigned int *my_peer_idx)
433 unsigned int local_peer_in_list;
434 /* number of peers in the normalized list */
436 struct GNUNET_PeerIdentity *normalized;
438 local_peer_in_list = GNUNET_YES;
440 if (peer_find (listed, num_listed, &my_peer) < 0)
442 local_peer_in_list = GNUNET_NO;
446 normalized = GNUNET_new_array (n,
447 struct GNUNET_PeerIdentity);
449 if (GNUNET_NO == local_peer_in_list)
450 normalized[n - 1] = my_peer;
452 GNUNET_memcpy (normalized,
454 num_listed * sizeof (struct GNUNET_PeerIdentity));
457 sizeof (struct GNUNET_PeerIdentity),
460 if (NULL != my_peer_idx)
461 *my_peer_idx = peer_find (normalized, n, &my_peer);
462 if (NULL != num_normalized)
470 * Get a the j-th lagrange coefficient for a set of indices.
472 * @param[out] coeff the lagrange coefficient
473 * @param j lagrange coefficient we want to compute
474 * @param indices indices
475 * @param num number of indices in @a indices
478 compute_lagrange_coefficient (gcry_mpi_t coeff, unsigned int j,
479 unsigned int *indices,
487 /* temp value for l-j */
490 GNUNET_assert (0 != coeff);
492 GNUNET_assert (0 != (n = gcry_mpi_new (0)));
493 GNUNET_assert (0 != (d = gcry_mpi_new (0)));
494 GNUNET_assert (0 != (tmp = gcry_mpi_new (0)));
496 gcry_mpi_set_ui (n, 1);
497 gcry_mpi_set_ui (d, 1);
499 for (i = 0; i < num; i++)
501 unsigned int l = indices[i];
504 gcry_mpi_mul_ui (n, n, l + 1);
506 gcry_mpi_set_ui (tmp, l + 1);
507 gcry_mpi_sub_ui (tmp, tmp, j + 1);
508 gcry_mpi_mul (d, d, tmp);
511 // gcry_mpi_invm does not like negative numbers ...
512 gcry_mpi_mod (d, d, elgamal_q);
514 GNUNET_assert (gcry_mpi_cmp_ui (d, 0) > 0);
516 // now we do the actual division, with everything mod q, as we
517 // are not operating on elements from <g>, but on exponents
518 GNUNET_assert (0 != gcry_mpi_invm (d, d, elgamal_q));
520 gcry_mpi_mulm (coeff, n, d, elgamal_q);
522 gcry_mpi_release (n);
523 gcry_mpi_release (d);
524 gcry_mpi_release (tmp);
529 * Destroy a decrypt session, removing it from
530 * the linked list of decrypt sessions.
532 * @param ds decrypt session to destroy
535 decrypt_session_destroy (struct DecryptSession *ds)
537 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
538 "destroying decrypt session\n");
541 ds->cs->decrypt_session = NULL;
544 if (NULL != ds->consensus)
546 GNUNET_CONSENSUS_destroy (ds->consensus);
547 ds->consensus = NULL;
550 if (NULL != ds->info)
552 for (unsigned int i = 0; i < ds->share->num_peers; i++)
554 if (NULL != ds->info[i].partial_decryption)
556 gcry_mpi_release (ds->info[i].partial_decryption);
557 ds->info[i].partial_decryption = NULL;
560 GNUNET_free (ds->info);
563 if (NULL != ds->share)
565 GNUNET_SECRETSHARING_share_destroy (ds->share);
574 keygen_info_destroy (struct KeygenPeerInfo *info)
576 if (NULL != info->sigma)
578 gcry_mpi_release (info->sigma);
581 if (NULL != info->presecret_commitment)
583 gcry_mpi_release (info->presecret_commitment);
584 info->presecret_commitment = NULL;
586 if (NULL != info->preshare_commitment)
588 gcry_mpi_release (info->preshare_commitment);
589 info->preshare_commitment = NULL;
595 keygen_session_destroy (struct KeygenSession *ks)
597 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
598 "destroying keygen session\n");
602 ks->cs->keygen_session = NULL;
605 if (NULL != ks->info)
607 for (unsigned int i = 0; i < ks->num_peers; i++)
608 keygen_info_destroy (&ks->info[i]);
609 GNUNET_free (ks->info);
613 if (NULL != ks->consensus)
615 GNUNET_CONSENSUS_destroy (ks->consensus);
616 ks->consensus = NULL;
619 if (NULL != ks->presecret_polynomial)
621 for (unsigned int i = 0; i < ks->threshold; i++)
623 GNUNET_assert (NULL != ks->presecret_polynomial[i]);
624 gcry_mpi_release (ks->presecret_polynomial[i]);
625 ks->presecret_polynomial[i] = NULL;
627 GNUNET_free (ks->presecret_polynomial);
628 ks->presecret_polynomial = NULL;
630 if (NULL != ks->my_share)
632 gcry_mpi_release (ks->my_share);
635 if (NULL != ks->public_key)
637 gcry_mpi_release (ks->public_key);
638 ks->public_key = NULL;
640 if (NULL != ks->peers)
642 GNUNET_free (ks->peers);
650 * Task run during shutdown.
656 cleanup_task (void *cls)
664 * Generate the random coefficients of our pre-secret polynomial
666 * @param ks the session
669 generate_presecret_polynomial (struct KeygenSession *ks)
674 GNUNET_assert (NULL == ks->presecret_polynomial);
675 ks->presecret_polynomial = GNUNET_new_array (ks->threshold,
677 for (i = 0; i < ks->threshold; i++)
679 v = ks->presecret_polynomial[i] = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS);
680 GNUNET_assert (NULL != v);
681 // Randomize v such that 0 < v < elgamal_q.
682 // The '- 1' is necessary as bitlength(q) = bitlength(p) - 1.
685 gcry_mpi_randomize (v, GNUNET_SECRETSHARING_ELGAMAL_BITS - 1, GCRY_WEAK_RANDOM);
686 } while ((gcry_mpi_cmp_ui (v, 0) == 0) || (gcry_mpi_cmp (v, elgamal_q) >= 0));
692 * Consensus element handler for round one.
693 * We should get one ephemeral key for each peer.
695 * @param cls Closure (keygen session).
696 * @param element The element from consensus, or
697 * NULL if consensus failed.
700 keygen_round1_new_element (void *cls,
701 const struct GNUNET_SET_Element *element)
703 const struct GNUNET_SECRETSHARING_KeygenCommitData *d;
704 struct KeygenSession *ks = cls;
705 struct KeygenPeerInfo *info;
709 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "round1 consensus failed\n");
713 /* elements have fixed size */
714 if (element->size != sizeof (struct GNUNET_SECRETSHARING_KeygenCommitData))
716 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
717 "keygen commit data with wrong size (%u) in consensus, %u expected\n",
718 (unsigned int) element->size,
719 (unsigned int) sizeof (struct GNUNET_SECRETSHARING_KeygenCommitData));
723 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "got round1 element\n");
726 info = get_keygen_peer_info (ks, &d->peer);
730 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong peer identity (%s) in consensus\n",
731 GNUNET_i2s (&d->peer));
735 /* Check that the right amount of data has been signed. */
736 if (d->purpose.size !=
737 htonl (element->size - offsetof (struct GNUNET_SECRETSHARING_KeygenCommitData, purpose)))
739 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong signature purpose size in consensus\n");
743 if (GNUNET_OK != GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG1,
744 &d->purpose, &d->signature, &d->peer.public_key))
746 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with invalid signature in consensus\n");
749 info->paillier_public_key = d->pubkey;
750 GNUNET_CRYPTO_mpi_scan_unsigned (&info->presecret_commitment, &d->commitment, 512 / 8);
751 info->round1_valid = GNUNET_YES;
756 * Evaluate the polynomial with coefficients @a coeff at @a x.
757 * The i-th element in @a coeff corresponds to the coefficient of x^i.
759 * @param[out] z result of the evaluation
760 * @param coeff array of coefficients
761 * @param num_coeff number of coefficients
762 * @param x where to evaluate the polynomial
763 * @param m what group are we operating in?
766 horner_eval (gcry_mpi_t z, gcry_mpi_t *coeff, unsigned int num_coeff, gcry_mpi_t x, gcry_mpi_t m)
770 gcry_mpi_set_ui (z, 0);
771 for (i = 0; i < num_coeff; i++)
774 gcry_mpi_mul (z, z, x);
775 gcry_mpi_addm (z, z, coeff[num_coeff - i - 1], m);
781 keygen_round2_conclude (void *cls)
783 struct KeygenSession *ks = cls;
784 struct GNUNET_SECRETSHARING_SecretReadyMessage *m;
785 struct GNUNET_MQ_Envelope *ev;
789 struct GNUNET_SECRETSHARING_Share *share;
791 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "round2 conclude\n");
793 GNUNET_CONSENSUS_destroy (ks->consensus);
794 ks->consensus = NULL;
796 share = GNUNET_new (struct GNUNET_SECRETSHARING_Share);
798 share->num_peers = 0;
800 for (i = 0; i < ks->num_peers; i++)
801 if (GNUNET_YES == ks->info[i].round2_valid)
804 share->peers = GNUNET_new_array (share->num_peers,
805 struct GNUNET_PeerIdentity);
807 GNUNET_new_array (share->num_peers,
808 struct GNUNET_SECRETSHARING_FieldElement);
809 share->original_indices = GNUNET_new_array (share->num_peers,
812 /* maybe we're not even in the list of peers? */
813 share->my_peer = share->num_peers;
815 j = 0; /* running index of valid peers */
816 for (i = 0; i < ks->num_peers; i++)
818 if (GNUNET_YES == ks->info[i].round2_valid)
820 share->peers[j] = ks->info[i].peer;
821 GNUNET_CRYPTO_mpi_print_unsigned (&share->sigmas[j],
822 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
824 share->original_indices[i] = j;
825 if (0 == memcmp (&share->peers[i], &my_peer, sizeof (struct GNUNET_PeerIdentity)))
831 if (share->my_peer == share->num_peers)
833 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "P%u: peer identity not in share\n", ks->local_peer_idx);
836 GNUNET_CRYPTO_mpi_print_unsigned (&share->my_share, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
838 GNUNET_CRYPTO_mpi_print_unsigned (&share->public_key, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
841 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "keygen completed with %u peers\n", share->num_peers);
843 /* Write the share. If 0 peers completed the dkg, an empty
844 * share will be sent. */
846 GNUNET_assert (GNUNET_OK == GNUNET_SECRETSHARING_share_write (share, NULL, 0, &share_size));
848 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "writing share of size %u\n",
849 (unsigned int) share_size);
851 ev = GNUNET_MQ_msg_extra (m, share_size,
852 GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_SECRET_READY);
854 GNUNET_assert (GNUNET_OK == GNUNET_SECRETSHARING_share_write (share, &m[1], share_size, NULL));
856 GNUNET_SECRETSHARING_share_destroy (share);
859 GNUNET_MQ_send (ks->cs->mq,
866 restore_fair (const struct GNUNET_CRYPTO_PaillierPublicKey *ppub,
867 const struct GNUNET_SECRETSHARING_FairEncryption *fe,
868 gcry_mpi_t x, gcry_mpi_t xres)
885 GNUNET_assert (NULL != (n = gcry_mpi_new (0)));
886 GNUNET_assert (NULL != (t = gcry_mpi_new (0)));
887 GNUNET_assert (NULL != (t_1 = gcry_mpi_new (0)));
888 GNUNET_assert (NULL != (t_2 = gcry_mpi_new (0)));
889 GNUNET_assert (NULL != (r = gcry_mpi_new (0)));
890 GNUNET_assert (NULL != (big_t = gcry_mpi_new (0)));
891 GNUNET_assert (NULL != (v = gcry_mpi_new (0)));
892 GNUNET_assert (NULL != (big_a = gcry_mpi_new (0)));
893 GNUNET_assert (NULL != (big_b = gcry_mpi_new (0)));
896 GNUNET_CRYPTO_mpi_scan_unsigned (&a_1, ppub, sizeof (struct GNUNET_CRYPTO_PaillierPublicKey));
897 GNUNET_assert (NULL != (a_2 = gcry_mpi_new (0)));
898 gcry_mpi_set_ui (a_2, 0);
900 GNUNET_assert (NULL != (b_1 = gcry_mpi_new (0)));
901 gcry_mpi_set (b_1, x);
902 GNUNET_assert (NULL != (b_2 = gcry_mpi_new (0)));
903 gcry_mpi_set_ui (b_2, 1);
906 gcry_mpi_mul (t, a_1, a_1);
907 gcry_mpi_mul (big_a, a_2, a_2);
908 gcry_mpi_add (big_a, big_a, t);
911 gcry_mpi_mul (t, b_1, b_1);
912 gcry_mpi_mul (big_b, b_2, b_2);
913 gcry_mpi_add (big_b, big_b, t);
918 gcry_mpi_mul (t, a_1, b_1);
919 gcry_mpi_mul (n, a_2, b_2);
920 gcry_mpi_add (n, n, t);
923 gcry_mpi_div (r, NULL, n, big_b, 0);
925 // T := A - 2rn + rrB
926 gcry_mpi_mul (v, r, n);
927 gcry_mpi_mul_ui (v, v, 2);
928 gcry_mpi_sub (big_t, big_a, v);
929 gcry_mpi_mul (v, r, r);
930 gcry_mpi_mul (v, v, big_b);
931 gcry_mpi_add (big_t, big_t, v);
933 if (gcry_mpi_cmp (big_t, big_b) >= 0)
939 gcry_mpi_mul (v, r, b_1);
940 gcry_mpi_sub (t_1, a_1, v);
941 gcry_mpi_mul (v, r, b_2);
942 gcry_mpi_sub (t_2, a_2, v);
945 gcry_mpi_set (a_1, b_1);
946 gcry_mpi_set (a_2, b_2);
948 gcry_mpi_set (b_1, t_1);
949 gcry_mpi_set (b_2, t_2);
951 gcry_mpi_set (big_a, big_b);
952 gcry_mpi_set (big_b, big_t);
956 gcry_mpi_t paillier_n;
958 GNUNET_CRYPTO_mpi_scan_unsigned (&paillier_n, ppub, sizeof (struct GNUNET_CRYPTO_PaillierPublicKey));
960 gcry_mpi_set (xres, b_2);
961 gcry_mpi_invm (xres, xres, elgamal_q);
962 gcry_mpi_mulm (xres, xres, b_1, elgamal_q);
965 gcry_mpi_release (a_1);
966 gcry_mpi_release (a_2);
967 gcry_mpi_release (b_1);
968 gcry_mpi_release (b_2);
969 gcry_mpi_release (big_a);
970 gcry_mpi_release (big_b);
971 gcry_mpi_release (big_t);
972 gcry_mpi_release (n);
973 gcry_mpi_release (t_1);
974 gcry_mpi_release (t_2);
975 gcry_mpi_release (t);
976 gcry_mpi_release (r);
977 gcry_mpi_release (v);
982 get_fair_encryption_challenge (const struct GNUNET_SECRETSHARING_FairEncryption *fe, gcry_mpi_t e)
985 struct GNUNET_CRYPTO_PaillierCiphertext c;
986 char h[GNUNET_SECRETSHARING_ELGAMAL_BITS / 8];
987 char t1[GNUNET_SECRETSHARING_ELGAMAL_BITS / 8];
988 char t2[GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8];
990 struct GNUNET_HashCode e_hash;
992 GNUNET_memcpy (&hash_data.c, &fe->c, sizeof (struct GNUNET_CRYPTO_PaillierCiphertext));
993 GNUNET_memcpy (&hash_data.h, &fe->h, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
994 GNUNET_memcpy (&hash_data.t1, &fe->t1, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
995 GNUNET_memcpy (&hash_data.t2, &fe->t2, GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8);
997 GNUNET_CRYPTO_mpi_scan_unsigned (&e, &e_hash, sizeof (struct GNUNET_HashCode));
998 gcry_mpi_mod (e, e, elgamal_q);
1003 verify_fair (const struct GNUNET_CRYPTO_PaillierPublicKey *ppub, const struct GNUNET_SECRETSHARING_FairEncryption *fe)
1018 GNUNET_assert (NULL != (n_sq = gcry_mpi_new (0)));
1019 GNUNET_assert (NULL != (tmp1 = gcry_mpi_new (0)));
1020 GNUNET_assert (NULL != (tmp2 = gcry_mpi_new (0)));
1021 GNUNET_assert (NULL != (e = gcry_mpi_new (0)));
1023 get_fair_encryption_challenge (fe, e);
1025 GNUNET_CRYPTO_mpi_scan_unsigned (&n, ppub, sizeof (struct GNUNET_CRYPTO_PaillierPublicKey));
1026 GNUNET_CRYPTO_mpi_scan_unsigned (&t1, fe->t1, GNUNET_CRYPTO_PAILLIER_BITS / 8);
1027 GNUNET_CRYPTO_mpi_scan_unsigned (&z, fe->z, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1028 GNUNET_CRYPTO_mpi_scan_unsigned (&y, fe->h, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1029 GNUNET_CRYPTO_mpi_scan_unsigned (&w, fe->w, GNUNET_CRYPTO_PAILLIER_BITS / 8);
1030 GNUNET_CRYPTO_mpi_scan_unsigned (&big_y, fe->c.bits, GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8);
1031 GNUNET_CRYPTO_mpi_scan_unsigned (&t2, fe->t2, GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8);
1032 gcry_mpi_mul (n_sq, n, n);
1035 gcry_mpi_powm (tmp1, elgamal_g, z, elgamal_p);
1037 gcry_mpi_powm (tmp1, y, e, elgamal_p);
1038 gcry_mpi_invm (tmp1, tmp1, elgamal_p);
1039 // tmp1 = tmp1 * tmp2
1040 gcry_mpi_mulm (tmp1, tmp1, tmp2, elgamal_p);
1042 if (0 == gcry_mpi_cmp (t1, tmp1))
1044 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "fair encryption invalid (t1)\n");
1049 gcry_mpi_powm (big_y, big_y, e, n_sq);
1050 gcry_mpi_invm (big_y, big_y, n_sq);
1052 gcry_mpi_add_ui (tmp1, n, 1);
1053 gcry_mpi_powm (tmp1, tmp1, z, n_sq);
1055 gcry_mpi_powm (tmp2, w, n, n_sq);
1057 gcry_mpi_mulm (tmp1, tmp1, tmp2, n_sq);
1058 gcry_mpi_mulm (tmp1, tmp1, big_y, n_sq);
1061 if (0 == gcry_mpi_cmp (t2, tmp1))
1063 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "fair encryption invalid (t2)\n");
1072 gcry_mpi_release (n);
1073 gcry_mpi_release (n_sq);
1074 gcry_mpi_release (z);
1075 gcry_mpi_release (t1);
1076 gcry_mpi_release (t2);
1077 gcry_mpi_release (e);
1078 gcry_mpi_release (w);
1079 gcry_mpi_release (tmp1);
1080 gcry_mpi_release (tmp2);
1081 gcry_mpi_release (y);
1082 gcry_mpi_release (big_y);
1088 * Create a fair Paillier encryption of then given ciphertext.
1090 * @param v the ciphertext
1091 * @param[out] fe the fair encryption
1094 encrypt_fair (gcry_mpi_t v, const struct GNUNET_CRYPTO_PaillierPublicKey *ppub, struct GNUNET_SECRETSHARING_FairEncryption *fe)
1109 GNUNET_assert (NULL != (r = gcry_mpi_new (0)));
1110 GNUNET_assert (NULL != (s = gcry_mpi_new (0)));
1111 GNUNET_assert (NULL != (t1 = gcry_mpi_new (0)));
1112 GNUNET_assert (NULL != (t2 = gcry_mpi_new (0)));
1113 GNUNET_assert (NULL != (z = gcry_mpi_new (0)));
1114 GNUNET_assert (NULL != (w = gcry_mpi_new (0)));
1115 GNUNET_assert (NULL != (n_sq = gcry_mpi_new (0)));
1116 GNUNET_assert (NULL != (e = gcry_mpi_new (0)));
1117 GNUNET_assert (NULL != (u = gcry_mpi_new (0)));
1118 GNUNET_assert (NULL != (Y = gcry_mpi_new (0)));
1119 GNUNET_assert (NULL != (G = gcry_mpi_new (0)));
1120 GNUNET_assert (NULL != (h = gcry_mpi_new (0)));
1122 GNUNET_CRYPTO_mpi_scan_unsigned (&n, ppub, sizeof (struct GNUNET_CRYPTO_PaillierPublicKey));
1123 gcry_mpi_mul (n_sq, n, n);
1124 gcry_mpi_add_ui (G, n, 1);
1127 gcry_mpi_randomize (u, GNUNET_CRYPTO_PAILLIER_BITS, GCRY_WEAK_RANDOM);
1129 while (gcry_mpi_cmp (u, n) >= 0);
1131 gcry_mpi_powm (t1, G, v, n_sq);
1132 gcry_mpi_powm (t2, u, n, n_sq);
1133 gcry_mpi_mulm (Y, t1, t2, n_sq);
1135 GNUNET_CRYPTO_mpi_print_unsigned (fe->c.bits,
1140 gcry_mpi_randomize (r, 2048, GCRY_WEAK_RANDOM);
1142 gcry_mpi_randomize (s, GNUNET_CRYPTO_PAILLIER_BITS, GCRY_WEAK_RANDOM);
1144 while (gcry_mpi_cmp (s, n) >= 0);
1147 gcry_mpi_mulm (t1, elgamal_g, r, elgamal_p);
1148 // compute t2 (use z and w as temp)
1149 gcry_mpi_powm (z, G, r, n_sq);
1150 gcry_mpi_powm (w, s, n, n_sq);
1151 gcry_mpi_mulm (t2, z, w, n_sq);
1154 gcry_mpi_powm (h, elgamal_g, v, elgamal_p);
1156 GNUNET_CRYPTO_mpi_print_unsigned (fe->h,
1157 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
1160 GNUNET_CRYPTO_mpi_print_unsigned (fe->t1,
1161 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
1164 GNUNET_CRYPTO_mpi_print_unsigned (fe->t2,
1165 GNUNET_CRYPTO_PAILLIER_BITS * 2 / 8,
1169 get_fair_encryption_challenge (fe, e);
1172 gcry_mpi_mul (z, e, v);
1173 gcry_mpi_addm (z, z, r, elgamal_q);
1175 gcry_mpi_powm (w, u, e, n);
1176 gcry_mpi_mulm (w, w, s, n);
1178 GNUNET_CRYPTO_mpi_print_unsigned (fe->z,
1179 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8,
1182 GNUNET_CRYPTO_mpi_print_unsigned (fe->w,
1183 GNUNET_CRYPTO_PAILLIER_BITS / 8,
1186 gcry_mpi_release (n);
1187 gcry_mpi_release (r);
1188 gcry_mpi_release (s);
1189 gcry_mpi_release (t1);
1190 gcry_mpi_release (t2);
1191 gcry_mpi_release (z);
1192 gcry_mpi_release (w);
1193 gcry_mpi_release (e);
1194 gcry_mpi_release (n_sq);
1195 gcry_mpi_release (u);
1196 gcry_mpi_release (Y);
1197 gcry_mpi_release (G);
1198 gcry_mpi_release (h);
1203 * Insert round 2 element in the consensus, consisting of
1204 * (1) The exponentiated pre-share polynomial coefficients A_{i,l}=g^{a_{i,l}}
1205 * (2) The exponentiated pre-shares y_{i,j}=g^{s_{i,j}}
1206 * (3) The encrypted pre-shares Y_{i,j}
1207 * (4) The zero knowledge proof for fairness of
1210 * @param ks session to use
1213 insert_round2_element (struct KeygenSession *ks)
1215 struct GNUNET_SET_Element *element;
1216 struct GNUNET_SECRETSHARING_KeygenRevealData *d;
1218 unsigned char *last_pos;
1219 size_t element_size;
1224 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting round2 element\n",
1225 ks->local_peer_idx);
1227 GNUNET_assert (NULL != (v = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
1228 GNUNET_assert (NULL != (idx = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
1230 element_size = (sizeof (struct GNUNET_SECRETSHARING_KeygenRevealData) +
1231 sizeof (struct GNUNET_SECRETSHARING_FairEncryption) * ks->num_peers +
1232 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->threshold);
1234 element = GNUNET_malloc (sizeof (struct GNUNET_SET_Element) + element_size);
1235 element->size = element_size;
1236 element->data = (void *) &element[1];
1238 d = (void *) element->data;
1241 // start inserting vector elements
1242 // after the fixed part of the element's data
1243 pos = (void *) &d[1];
1244 last_pos = pos + element_size;
1246 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed exp preshares\n",
1247 ks->local_peer_idx);
1249 // encrypted pre-shares
1250 // and fair encryption proof
1252 for (i = 0; i < ks->num_peers; i++)
1254 ptrdiff_t remaining = last_pos - pos;
1255 struct GNUNET_SECRETSHARING_FairEncryption *fe = (void *) pos;
1257 GNUNET_assert (remaining > 0);
1258 memset (fe, 0, sizeof *fe);
1259 if (GNUNET_YES == ks->info[i].round1_valid)
1261 gcry_mpi_set_ui (idx, i + 1);
1262 // evaluate the polynomial
1263 horner_eval (v, ks->presecret_polynomial, ks->threshold, idx, elgamal_q);
1264 // encrypt the result
1265 encrypt_fair (v, &ks->info[i].paillier_public_key, fe);
1271 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed enc preshares\n",
1272 ks->local_peer_idx);
1274 // exponentiated coefficients
1275 for (i = 0; i < ks->threshold; i++)
1277 ptrdiff_t remaining = last_pos - pos;
1278 GNUNET_assert (remaining > 0);
1279 gcry_mpi_powm (v, elgamal_g, ks->presecret_polynomial[i], elgamal_p);
1280 GNUNET_CRYPTO_mpi_print_unsigned (pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
1281 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8;
1284 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: computed exp coefficients\n",
1285 ks->local_peer_idx);
1288 d->purpose.size = htonl (element_size - offsetof (struct GNUNET_SECRETSHARING_KeygenRevealData, purpose));
1289 d->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG2);
1290 GNUNET_assert (GNUNET_OK ==
1291 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key,
1295 GNUNET_CONSENSUS_insert (ks->consensus, element, NULL, NULL);
1296 GNUNET_free (element); /* FIXME: maybe stack-allocate instead? */
1298 gcry_mpi_release (v);
1299 gcry_mpi_release (idx);
1304 keygen_reveal_get_exp_coeff (struct KeygenSession *ks,
1305 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1309 gcry_mpi_t exp_coeff;
1311 GNUNET_assert (idx < ks->threshold);
1313 pos = (void *) &d[1];
1314 // skip encrypted pre-shares
1315 pos += sizeof (struct GNUNET_SECRETSHARING_FairEncryption) * ks->num_peers;
1316 // skip exp. coeffs we are not interested in
1317 pos += GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * idx;
1318 // the first exponentiated coefficient is the public key share
1319 GNUNET_CRYPTO_mpi_scan_unsigned (&exp_coeff, pos, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1324 static struct GNUNET_SECRETSHARING_FairEncryption *
1325 keygen_reveal_get_enc_preshare (struct KeygenSession *ks,
1326 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1331 GNUNET_assert (idx < ks->num_peers);
1333 pos = (void *) &d[1];
1334 // skip encrypted pre-shares we're not interested in
1335 pos += sizeof (struct GNUNET_SECRETSHARING_FairEncryption) * idx;
1336 return (struct GNUNET_SECRETSHARING_FairEncryption *) pos;
1341 keygen_reveal_get_exp_preshare (struct KeygenSession *ks,
1342 const struct GNUNET_SECRETSHARING_KeygenRevealData *d,
1345 gcry_mpi_t exp_preshare;
1346 struct GNUNET_SECRETSHARING_FairEncryption *fe;
1348 GNUNET_assert (idx < ks->num_peers);
1349 fe = keygen_reveal_get_enc_preshare (ks, d, idx);
1350 GNUNET_CRYPTO_mpi_scan_unsigned (&exp_preshare, fe->h, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1351 return exp_preshare;
1356 keygen_round2_new_element (void *cls,
1357 const struct GNUNET_SET_Element *element)
1359 struct KeygenSession *ks = cls;
1360 const struct GNUNET_SECRETSHARING_KeygenRevealData *d;
1361 struct KeygenPeerInfo *info;
1362 size_t expected_element_size;
1366 gcry_mpi_t public_key_share;
1367 gcry_mpi_t preshare;
1369 if (NULL == element)
1371 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "round2 consensus failed\n");
1375 expected_element_size = (sizeof (struct GNUNET_SECRETSHARING_KeygenRevealData) +
1376 sizeof (struct GNUNET_SECRETSHARING_FairEncryption) * ks->num_peers +
1377 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8 * ks->threshold);
1379 if (element->size != expected_element_size)
1381 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1382 "keygen round2 data with wrong size (%u) in consensus, %u expected\n",
1383 (unsigned int) element->size,
1384 (unsigned int) expected_element_size);
1388 d = (const void *) element->data;
1390 info = get_keygen_peer_info (ks, &d->peer);
1394 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen commit data with wrong peer identity (%s) in consensus\n",
1395 GNUNET_i2s (&d->peer));
1399 if (GNUNET_NO == info->round1_valid)
1401 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1402 "ignoring round2 element from peer with invalid round1 element (%s)\n",
1403 GNUNET_i2s (&d->peer));
1407 if (GNUNET_YES == info->round2_valid)
1409 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1410 "ignoring duplicate round2 element (%s)\n",
1411 GNUNET_i2s (&d->peer));
1415 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "got round2 element\n");
1417 if (ntohl (d->purpose.size) !=
1418 element->size - offsetof (struct GNUNET_SECRETSHARING_KeygenRevealData, purpose))
1420 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen reveal data with wrong signature purpose size in consensus\n");
1424 if (GNUNET_OK != GNUNET_CRYPTO_eddsa_verify (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG2,
1425 &d->purpose, &d->signature, &d->peer.public_key))
1427 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "keygen reveal data with invalid signature in consensus\n");
1431 public_key_share = keygen_reveal_get_exp_coeff (ks, d, 0);
1432 info->preshare_commitment = keygen_reveal_get_exp_preshare (ks, d, ks->local_peer_idx);
1434 if (NULL == ks->public_key)
1436 GNUNET_assert (NULL != (ks->public_key = gcry_mpi_new (0)));
1437 gcry_mpi_set_ui (ks->public_key, 1);
1439 gcry_mpi_mulm (ks->public_key, ks->public_key, public_key_share, elgamal_p);
1441 gcry_mpi_release (public_key_share);
1442 public_key_share = NULL;
1445 struct GNUNET_SECRETSHARING_FairEncryption *fe = keygen_reveal_get_enc_preshare (ks, d, ks->local_peer_idx);
1446 GNUNET_assert (NULL != (preshare = gcry_mpi_new (0)));
1447 GNUNET_CRYPTO_paillier_decrypt (&ks->paillier_private_key,
1448 &ks->info[ks->local_peer_idx].paillier_public_key,
1452 // FIXME: not doing the restoration is less expensive
1453 restore_fair (&ks->info[ks->local_peer_idx].paillier_public_key,
1459 GNUNET_assert (NULL != (tmp = gcry_mpi_new (0)));
1460 gcry_mpi_powm (tmp, elgamal_g, preshare, elgamal_p);
1462 cmp_result = gcry_mpi_cmp (tmp, info->preshare_commitment);
1463 gcry_mpi_release (tmp);
1465 if (0 != cmp_result)
1467 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: Got invalid presecret from P%u\n",
1468 (unsigned int) ks->local_peer_idx, (unsigned int) (info - ks->info));
1472 if (NULL == ks->my_share)
1474 GNUNET_assert (NULL != (ks->my_share = gcry_mpi_new (0)));
1476 gcry_mpi_addm (ks->my_share, ks->my_share, preshare, elgamal_q);
1478 for (j = 0; j < ks->num_peers; j++)
1480 gcry_mpi_t presigma;
1481 if (NULL == ks->info[j].sigma)
1483 GNUNET_assert (NULL != (ks->info[j].sigma = gcry_mpi_new (0)));
1484 gcry_mpi_set_ui (ks->info[j].sigma, 1);
1486 presigma = keygen_reveal_get_exp_preshare (ks, d, j);
1487 gcry_mpi_mulm (ks->info[j].sigma, ks->info[j].sigma, presigma, elgamal_p);
1488 gcry_mpi_release (presigma);
1492 GNUNET_assert (NULL != (prod = gcry_mpi_new (0)));
1494 GNUNET_assert (NULL != (j_to_k = gcry_mpi_new (0)));
1495 // validate that the polynomial sharing matches the additive sharing
1496 for (j = 0; j < ks->num_peers; j++)
1500 gcry_mpi_t exp_preshare;
1501 gcry_mpi_set_ui (prod, 1);
1502 for (k = 0; k < ks->threshold; k++)
1504 // Using pow(double,double) is a bit sketchy.
1505 // We count players from 1, but shares from 0.
1507 gcry_mpi_set_ui (j_to_k, (unsigned int) pow(j+1, k));
1508 tmp = keygen_reveal_get_exp_coeff (ks, d, k);
1509 gcry_mpi_powm (tmp, tmp, j_to_k, elgamal_p);
1510 gcry_mpi_mulm (prod, prod, tmp, elgamal_p);
1511 gcry_mpi_release (tmp);
1513 exp_preshare = keygen_reveal_get_exp_preshare (ks, d, j);
1514 gcry_mpi_mod (exp_preshare, exp_preshare, elgamal_p);
1515 cmp_result = gcry_mpi_cmp (prod, exp_preshare);
1516 gcry_mpi_release (exp_preshare);
1517 exp_preshare = NULL;
1518 if (0 != cmp_result)
1520 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: reveal data from P%u incorrect\n",
1521 ks->local_peer_idx, j);
1522 /* no need for further verification, round2 stays invalid ... */
1527 // TODO: verify proof of fair encryption (once implemented)
1528 for (j = 0; j < ks->num_peers; j++)
1530 struct GNUNET_SECRETSHARING_FairEncryption *fe = keygen_reveal_get_enc_preshare (ks, d, j);
1531 if (GNUNET_YES != verify_fair (&ks->info[j].paillier_public_key, fe))
1533 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: reveal data from P%u incorrect (fair encryption)\n",
1534 ks->local_peer_idx, j);
1540 info->round2_valid = GNUNET_YES;
1542 gcry_mpi_release (preshare);
1543 gcry_mpi_release (prod);
1544 gcry_mpi_release (j_to_k);
1549 * Called when the first consensus round has concluded.
1550 * Will initiate the second round.
1552 * @param cls closure
1555 keygen_round1_conclude (void *cls)
1557 struct KeygenSession *ks = cls;
1559 GNUNET_CONSENSUS_destroy (ks->consensus);
1561 ks->consensus = GNUNET_CONSENSUS_create (cfg, ks->num_peers, ks->peers, &ks->session_id,
1562 time_between (ks->start_time, ks->deadline, 1, 2),
1564 keygen_round2_new_element, ks);
1566 insert_round2_element (ks);
1568 GNUNET_CONSENSUS_conclude (ks->consensus,
1569 keygen_round2_conclude,
1575 * Insert the ephemeral key and the presecret commitment
1576 * of this peer in the consensus of the given session.
1578 * @param ks session to use
1581 insert_round1_element (struct KeygenSession *ks)
1583 struct GNUNET_SET_Element *element;
1584 struct GNUNET_SECRETSHARING_KeygenCommitData *d;
1587 // big-endian representation of 'v'
1588 unsigned char v_data[GNUNET_SECRETSHARING_ELGAMAL_BITS / 8];
1590 element = GNUNET_malloc (sizeof *element + sizeof *d);
1591 d = (void *) &element[1];
1593 element->size = sizeof *d;
1597 GNUNET_assert (0 != (v = gcry_mpi_new (GNUNET_SECRETSHARING_ELGAMAL_BITS)));
1599 gcry_mpi_powm (v, elgamal_g, ks->presecret_polynomial[0], elgamal_p);
1601 GNUNET_CRYPTO_mpi_print_unsigned (v_data, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, v);
1603 GNUNET_CRYPTO_hash (v_data, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, &d->commitment);
1605 d->pubkey = ks->info[ks->local_peer_idx].paillier_public_key;
1607 d->purpose.size = htonl ((sizeof *d) - offsetof (struct GNUNET_SECRETSHARING_KeygenCommitData, purpose));
1608 d->purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DKG1);
1609 GNUNET_assert (GNUNET_OK ==
1610 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key,
1614 GNUNET_CONSENSUS_insert (ks->consensus, element, NULL, NULL);
1616 gcry_mpi_release (v);
1617 GNUNET_free (element);
1622 * Check that @a msg is well-formed.
1624 * @param cls identification of the client
1625 * @param msg the actual message
1626 * @return #GNUNET_OK if @a msg is well-formed
1629 check_client_keygen (void *cls,
1630 const struct GNUNET_SECRETSHARING_CreateMessage *msg)
1632 unsigned int num_peers = ntohs (msg->num_peers);
1634 if (ntohs (msg->header.size) - sizeof (*msg) !=
1635 num_peers * sizeof (struct GNUNET_PeerIdentity))
1638 return GNUNET_SYSERR;
1645 * Functions with this signature are called whenever a message is
1648 * @param cls identification of the client
1649 * @param msg the actual message
1652 handle_client_keygen (void *cls,
1653 const struct GNUNET_SECRETSHARING_CreateMessage *msg)
1655 struct ClientState *cs = cls;
1656 struct KeygenSession *ks;
1658 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
1659 "client requested key generation\n");
1660 if (NULL != cs->keygen_session)
1663 GNUNET_SERVICE_client_drop (cs->client);
1666 ks = GNUNET_new (struct KeygenSession);
1668 cs->keygen_session = ks;
1669 ks->deadline = GNUNET_TIME_absolute_ntoh (msg->deadline);
1670 ks->threshold = ntohs (msg->threshold);
1671 ks->num_peers = ntohs (msg->num_peers);
1673 ks->peers = normalize_peers ((struct GNUNET_PeerIdentity *) &msg[1],
1676 &ks->local_peer_idx);
1679 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
1680 "first round of consensus with %u peers\n",
1682 ks->consensus = GNUNET_CONSENSUS_create (cfg,
1686 GNUNET_TIME_absolute_ntoh (msg->start),
1687 GNUNET_TIME_absolute_ntoh (msg->deadline),
1688 keygen_round1_new_element,
1691 ks->info = GNUNET_new_array (ks->num_peers,
1692 struct KeygenPeerInfo);
1694 for (unsigned int i = 0; i < ks->num_peers; i++)
1695 ks->info[i].peer = ks->peers[i];
1697 GNUNET_CRYPTO_paillier_create (&ks->info[ks->local_peer_idx].paillier_public_key,
1698 &ks->paillier_private_key);
1700 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1701 "P%u: Generated paillier key pair\n",
1702 ks->local_peer_idx);
1703 generate_presecret_polynomial (ks);
1704 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1705 "P%u: Generated presecret polynomial\n",
1706 ks->local_peer_idx);
1707 insert_round1_element (ks);
1708 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1709 "P%u: Concluding for round 1\n",
1710 ks->local_peer_idx);
1711 GNUNET_CONSENSUS_conclude (ks->consensus,
1712 keygen_round1_conclude,
1714 GNUNET_SERVICE_client_continue (cs->client);
1715 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1716 "P%u: Waiting for round 1 elements ...\n",
1717 ks->local_peer_idx);
1722 * Called when the partial decryption consensus concludes.
1725 decrypt_conclude (void *cls)
1727 struct DecryptSession *ds = cls;
1728 struct GNUNET_SECRETSHARING_DecryptResponseMessage *msg;
1729 struct GNUNET_MQ_Envelope *ev;
1730 gcry_mpi_t lagrange;
1735 unsigned int *indices;
1740 GNUNET_CONSENSUS_destroy (ds->consensus);
1741 ds->consensus = NULL;
1743 GNUNET_assert (0 != (lagrange = gcry_mpi_new (0)));
1744 GNUNET_assert (0 != (m = gcry_mpi_new (0)));
1745 GNUNET_assert (0 != (tmp = gcry_mpi_new (0)));
1746 GNUNET_assert (0 != (prod = gcry_mpi_new (0)));
1749 for (i = 0; i < ds->share->num_peers; i++)
1750 if (NULL != ds->info[i].partial_decryption)
1753 indices = GNUNET_new_array (num,
1756 for (i = 0; i < ds->share->num_peers; i++)
1757 if (NULL != ds->info[i].partial_decryption)
1758 indices[j++] = ds->info[i].original_index;
1760 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
1761 "P%u: decrypt conclude, with %u peers\n",
1765 gcry_mpi_set_ui (prod, 1);
1766 for (i = 0; i < num; i++)
1769 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
1770 "P%u: index of %u: %u\n",
1771 ds->share->my_peer, i, indices[i]);
1772 compute_lagrange_coefficient (lagrange, indices[i], indices, num);
1774 gcry_mpi_powm (tmp, ds->info[indices[i]].partial_decryption, lagrange, elgamal_p);
1776 // product of all exponentiated partiel decryptions ...
1777 gcry_mpi_mulm (prod, prod, tmp, elgamal_p);
1780 GNUNET_CRYPTO_mpi_scan_unsigned (&c_2, ds->ciphertext.c2_bits, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1782 GNUNET_assert (0 != gcry_mpi_invm (prod, prod, elgamal_p));
1783 gcry_mpi_mulm (m, c_2, prod, elgamal_p);
1784 ev = GNUNET_MQ_msg (msg, GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_DECRYPT_DONE);
1785 GNUNET_CRYPTO_mpi_print_unsigned (&msg->plaintext, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, m);
1786 msg->success = htonl (1);
1787 GNUNET_MQ_send (ds->cs->mq,
1790 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "sent decrypt done to client\n");
1792 GNUNET_free (indices);
1794 gcry_mpi_release(lagrange);
1795 gcry_mpi_release(m);
1796 gcry_mpi_release(tmp);
1797 gcry_mpi_release(prod);
1798 gcry_mpi_release(c_2);
1800 // FIXME: what if not enough peers participated?
1805 * Get a string representation of an MPI.
1806 * The caller must free the returned string.
1808 * @param mpi mpi to convert to a string
1809 * @return string representation of @a mpi, must be free'd by the caller
1812 mpi_to_str (gcry_mpi_t mpi)
1816 GNUNET_assert (0 == gcry_mpi_aprint (GCRYMPI_FMT_HEX, &buf, NULL, mpi));
1817 return (char *) buf;
1822 * Called when a new partial decryption arrives.
1825 decrypt_new_element (void *cls,
1826 const struct GNUNET_SET_Element *element)
1828 struct DecryptSession *session = cls;
1829 const struct GNUNET_SECRETSHARING_DecryptData *d;
1830 struct DecryptPeerInfo *info;
1831 struct GNUNET_HashCode challenge_hash;
1835 /* nizk challenge */
1836 gcry_mpi_t challenge;
1837 /* nizk commit1, g^\beta */
1839 /* nizk commit2, c_1^\beta */
1841 /* homomorphic commitment to the peer's share,
1842 * public key share */
1844 /* partial decryption we received */
1846 /* ciphertext component #1 */
1848 /* temporary variable (for comparision) #1 */
1850 /* temporary variable (for comparision) #2 */
1853 if (NULL == element)
1855 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decryption failed\n");
1856 /* FIXME: destroy */
1860 if (element->size != sizeof *d)
1862 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "element of wrong size in decrypt consensus\n");
1868 info = get_decrypt_peer_info (session, &d->peer);
1872 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decrypt element from invalid peer (%s)\n",
1873 GNUNET_i2s (&d->peer));
1877 if (NULL != info->partial_decryption)
1879 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "decrypt element duplicate\n");
1883 if (0 != memcmp (&d->ciphertext, &session->ciphertext, sizeof (struct GNUNET_SECRETSHARING_Ciphertext)))
1885 GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: got decrypt element with non-matching ciphertext from P%u\n",
1886 (unsigned int) session->share->my_peer, (unsigned int) (info - session->info));
1892 GNUNET_CRYPTO_hash (offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext) + (char *) d,
1893 offsetof (struct GNUNET_SECRETSHARING_DecryptData, nizk_response) -
1894 offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext),
1897 GNUNET_CRYPTO_mpi_scan_unsigned (&challenge, &challenge_hash,
1898 sizeof (struct GNUNET_HashCode));
1900 GNUNET_CRYPTO_mpi_scan_unsigned (&sigma, &session->share->sigmas[info - session->info],
1901 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1903 GNUNET_CRYPTO_mpi_scan_unsigned (&c1, session->ciphertext.c1_bits,
1904 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1906 GNUNET_CRYPTO_mpi_scan_unsigned (&commit1, &d->nizk_commit1,
1907 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1909 GNUNET_CRYPTO_mpi_scan_unsigned (&commit2, &d->nizk_commit2,
1910 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1912 GNUNET_CRYPTO_mpi_scan_unsigned (&r, &d->nizk_response,
1913 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1915 GNUNET_CRYPTO_mpi_scan_unsigned (&w, &d->partial_decryption,
1916 sizeof (struct GNUNET_SECRETSHARING_FieldElement));
1918 GNUNET_assert (NULL != (tmp1 = gcry_mpi_new (0)));
1919 GNUNET_assert (NULL != (tmp2 = gcry_mpi_new (0)));
1922 gcry_mpi_powm (tmp1, elgamal_g, r, elgamal_p);
1924 // tmp2 = g^\beta * \sigma^challenge
1925 gcry_mpi_powm (tmp2, sigma, challenge, elgamal_p);
1926 gcry_mpi_mulm (tmp2, tmp2, commit1, elgamal_p);
1928 if (0 != gcry_mpi_cmp (tmp1, tmp2))
1933 tmp1_str = mpi_to_str (tmp1);
1934 tmp2_str = mpi_to_str (tmp2);
1935 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1936 "P%u: Received invalid partial decryption from P%u (eqn 1), expected %s got %s\n",
1937 session->share->my_peer,
1938 (unsigned int) (info - session->info),
1941 GNUNET_free (tmp1_str);
1942 GNUNET_free (tmp2_str);
1947 gcry_mpi_powm (tmp1, c1, r, elgamal_p);
1949 gcry_mpi_powm (tmp2, w, challenge, elgamal_p);
1950 gcry_mpi_mulm (tmp2, tmp2, commit2, elgamal_p);
1953 if (0 != gcry_mpi_cmp (tmp1, tmp2))
1955 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1956 "P%u: Received invalid partial decryption from P%u (eqn 2)\n",
1957 session->share->my_peer,
1958 (unsigned int) (info - session->info));
1963 GNUNET_CRYPTO_mpi_scan_unsigned (&info->partial_decryption, &d->partial_decryption,
1964 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
1966 gcry_mpi_release (tmp1);
1967 gcry_mpi_release (tmp2);
1968 gcry_mpi_release (sigma);
1969 gcry_mpi_release (commit1);
1970 gcry_mpi_release (commit2);
1971 gcry_mpi_release (r);
1972 gcry_mpi_release (w);
1973 gcry_mpi_release (challenge);
1974 gcry_mpi_release (c1);
1979 insert_decrypt_element (struct DecryptSession *ds)
1981 struct GNUNET_SECRETSHARING_DecryptData d;
1982 struct GNUNET_SET_Element element;
1985 /* partial decryption with our share */
1987 /* first component of the elgamal ciphertext */
1989 /* nonce for dlog zkp */
1992 gcry_mpi_t challenge;
1994 struct GNUNET_HashCode challenge_hash;
1996 /* make vagrind happy until we implement the real deal ... */
1997 memset (&d, 0, sizeof d);
1999 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: Inserting decrypt element\n",
2000 ds->share->my_peer);
2002 GNUNET_assert (ds->share->my_peer < ds->share->num_peers);
2004 GNUNET_CRYPTO_mpi_scan_unsigned (&c1, &ds->ciphertext.c1_bits,
2005 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
2006 GNUNET_CRYPTO_mpi_scan_unsigned (&s, &ds->share->my_share,
2007 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
2008 GNUNET_CRYPTO_mpi_scan_unsigned (&sigma, &ds->share->sigmas[ds->share->my_peer],
2009 GNUNET_SECRETSHARING_ELGAMAL_BITS / 8);
2011 GNUNET_assert (NULL != (w = gcry_mpi_new (0)));
2012 GNUNET_assert (NULL != (beta = gcry_mpi_new (0)));
2013 GNUNET_assert (NULL != (tmp = gcry_mpi_new (0)));
2015 // FIXME: unnecessary, remove once crypto works
2016 gcry_mpi_powm (tmp, elgamal_g, s, elgamal_p);
2017 if (0 != gcry_mpi_cmp (tmp, sigma))
2019 char *sigma_str = mpi_to_str (sigma);
2020 char *tmp_str = mpi_to_str (tmp);
2021 char *s_str = mpi_to_str (s);
2022 GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "Share of P%u is invalid, ref sigma %s, "
2023 "computed sigma %s, s %s\n",
2025 sigma_str, tmp_str, s_str);
2026 GNUNET_free (sigma_str);
2027 GNUNET_free (tmp_str);
2028 GNUNET_free (s_str);
2031 gcry_mpi_powm (w, c1, s, elgamal_p);
2033 element.data = (void *) &d;
2034 element.size = sizeof (struct GNUNET_SECRETSHARING_DecryptData);
2035 element.element_type = 0;
2037 d.ciphertext = ds->ciphertext;
2039 GNUNET_CRYPTO_mpi_print_unsigned (&d.partial_decryption, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, w);
2041 // create the zero knowledge proof
2042 // randomly choose beta such that 0 < beta < q
2045 gcry_mpi_randomize (beta, GNUNET_SECRETSHARING_ELGAMAL_BITS - 1, GCRY_WEAK_RANDOM);
2046 } while ((gcry_mpi_cmp_ui (beta, 0) == 0) || (gcry_mpi_cmp (beta, elgamal_q) >= 0));
2048 gcry_mpi_powm (tmp, elgamal_g, beta, elgamal_p);
2049 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_commit1, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
2051 gcry_mpi_powm (tmp, c1, beta, elgamal_p);
2052 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_commit2, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
2054 // the challenge is the hash of everything up to the response
2055 GNUNET_CRYPTO_hash (offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext) + (char *) &d,
2056 offsetof (struct GNUNET_SECRETSHARING_DecryptData, nizk_response) -
2057 offsetof (struct GNUNET_SECRETSHARING_DecryptData, ciphertext),
2060 GNUNET_CRYPTO_mpi_scan_unsigned (&challenge, &challenge_hash,
2061 sizeof (struct GNUNET_HashCode));
2063 // compute the response in tmp,
2064 // tmp = (c * s + beta) mod q
2065 gcry_mpi_mulm (tmp, challenge, s, elgamal_q);
2066 gcry_mpi_addm (tmp, tmp, beta, elgamal_q);
2068 GNUNET_CRYPTO_mpi_print_unsigned (&d.nizk_response, GNUNET_SECRETSHARING_ELGAMAL_BITS / 8, tmp);
2070 d.purpose.size = htonl (element.size - offsetof (struct GNUNET_SECRETSHARING_DecryptData, purpose));
2071 d.purpose.purpose = htonl (GNUNET_SIGNATURE_PURPOSE_SECRETSHARING_DECRYPTION);
2073 GNUNET_assert (GNUNET_OK ==
2074 GNUNET_CRYPTO_eddsa_sign (my_peer_private_key,
2078 GNUNET_CONSENSUS_insert (ds->consensus, &element, NULL, NULL);
2079 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
2080 "P%u: Inserting decrypt element done!\n",
2081 ds->share->my_peer);
2083 gcry_mpi_release (s);
2084 gcry_mpi_release (w);
2085 gcry_mpi_release (c1);
2086 gcry_mpi_release (beta);
2087 gcry_mpi_release (tmp);
2088 gcry_mpi_release (challenge);
2089 gcry_mpi_release (sigma);
2094 * Check that @a msg is well-formed.
2096 * @param cls identification of the client
2097 * @param msg the actual message
2098 * @return #GNUNET_OK (check deferred a bit)
2101 check_client_decrypt (void *cls,
2102 const struct GNUNET_SECRETSHARING_DecryptRequestMessage *msg)
2104 /* we check later, it's complicated */
2110 * Functions with this signature are called whenever a message is
2113 * @param cls identification of the client
2114 * @param msg the actual message
2117 handle_client_decrypt (void *cls,
2118 const struct GNUNET_SECRETSHARING_DecryptRequestMessage *msg)
2120 struct ClientState *cs = cls;
2121 struct DecryptSession *ds;
2122 struct GNUNET_HashCode session_id;
2124 if (NULL != cs->decrypt_session)
2127 GNUNET_SERVICE_client_drop (cs->client);
2130 ds = GNUNET_new (struct DecryptSession);
2131 cs->decrypt_session = ds;
2133 ds->start = GNUNET_TIME_absolute_ntoh (msg->start);
2134 ds->deadline = GNUNET_TIME_absolute_ntoh (msg->deadline);
2135 ds->ciphertext = msg->ciphertext;
2137 ds->share = GNUNET_SECRETSHARING_share_read (&msg[1],
2138 ntohs (msg->header.size) - sizeof (*msg),
2140 if (NULL == ds->share)
2143 GNUNET_SERVICE_client_drop (cs->client);
2147 /* FIXME: this is probably sufficient, but kdf/hash with all values would be nicer ... */
2148 GNUNET_CRYPTO_hash (&msg->ciphertext,
2149 sizeof (struct GNUNET_SECRETSHARING_Ciphertext),
2151 ds->consensus = GNUNET_CONSENSUS_create (cfg,
2152 ds->share->num_peers,
2157 &decrypt_new_element,
2161 ds->info = GNUNET_new_array (ds->share->num_peers,
2162 struct DecryptPeerInfo);
2163 for (unsigned int i = 0; i < ds->share->num_peers; i++)
2165 ds->info[i].peer = ds->share->peers[i];
2166 ds->info[i].original_index = ds->share->original_indices[i];
2168 insert_decrypt_element (ds);
2169 GNUNET_CONSENSUS_conclude (ds->consensus,
2172 GNUNET_SERVICE_client_continue (cs->client);
2173 GNUNET_log (GNUNET_ERROR_TYPE_INFO,
2174 "decrypting with %u peers\n",
2175 ds->share->num_peers);
2180 init_crypto_constants (void)
2182 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_q, GCRYMPI_FMT_HEX,
2183 GNUNET_SECRETSHARING_ELGAMAL_Q_HEX, 0, NULL));
2184 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_p, GCRYMPI_FMT_HEX,
2185 GNUNET_SECRETSHARING_ELGAMAL_P_HEX, 0, NULL));
2186 GNUNET_assert (0 == gcry_mpi_scan (&elgamal_g, GCRYMPI_FMT_HEX,
2187 GNUNET_SECRETSHARING_ELGAMAL_G_HEX, 0, NULL));
2192 * Initialize secretsharing service.
2194 * @param cls closure
2195 * @param c configuration to use
2196 * @param service the initialized service
2200 const struct GNUNET_CONFIGURATION_Handle *c,
2201 struct GNUNET_SERVICE_Handle *service)
2204 my_peer_private_key = GNUNET_CRYPTO_eddsa_key_create_from_configuration (c);
2205 if (NULL == my_peer_private_key)
2207 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
2208 "could not access host private key\n");
2210 GNUNET_SCHEDULER_shutdown ();
2213 init_crypto_constants ();
2215 GNUNET_CRYPTO_get_peer_identity (cfg,
2218 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
2219 "could not retrieve host identity\n");
2221 GNUNET_SCHEDULER_shutdown ();
2224 GNUNET_SCHEDULER_add_shutdown (&cleanup_task,
2230 * Callback called when a client connects to the service.
2232 * @param cls closure for the service
2233 * @param c the new client that connected to the service
2234 * @param mq the message queue used to send messages to the client
2238 client_connect_cb (void *cls,
2239 struct GNUNET_SERVICE_Client *c,
2240 struct GNUNET_MQ_Handle *mq)
2242 struct ClientState *cs = GNUNET_new (struct ClientState);;
2251 * Callback called when a client disconnected from the service
2253 * @param cls closure for the service
2254 * @param c the client that disconnected
2255 * @param internal_cls should be equal to @a c
2258 client_disconnect_cb (void *cls,
2259 struct GNUNET_SERVICE_Client *c,
2262 struct ClientState *cs = internal_cls;
2264 if (NULL != cs->keygen_session)
2265 keygen_session_destroy (cs->keygen_session);
2267 if (NULL != cs->decrypt_session)
2268 decrypt_session_destroy (cs->decrypt_session);
2274 * Define "main" method using service macro.
2278 GNUNET_SERVICE_OPTION_NONE,
2281 &client_disconnect_cb,
2283 GNUNET_MQ_hd_var_size (client_keygen,
2284 GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_GENERATE,
2285 struct GNUNET_SECRETSHARING_CreateMessage,
2287 GNUNET_MQ_hd_var_size (client_decrypt,
2288 GNUNET_MESSAGE_TYPE_SECRETSHARING_CLIENT_DECRYPT,
2289 struct GNUNET_SECRETSHARING_DecryptRequestMessage,
2291 GNUNET_MQ_handler_end ());