Refactor keygen tests and add signing tests

Author: jesseposner

src/modules/frost/tests_impl.h

@@ -4,84 +4,139 @@
 #include "include/secp256k1_frost.h"
 #include <secp256k1_musig.h>
 
+ /* Number of public keys involved in creating the aggregate signature */
+#define N_SIGNERS 3
+
+ /* Threshold required in creating the aggregate signature */
+#define THRESHOLD 2
+
 void run_frost_tests(void) {
-    unsigned char sk1[32];
-    unsigned char sk2[32];
-    unsigned char sk3[32];
-    unsigned char pk1[32];
-    unsigned char pk2[32];
-    size_t participants[2];
-    secp256k1_scalar coefficients1[2];
-    secp256k1_scalar coefficients2[2];
-    secp256k1_scalar coefficients3[2];
-    secp256k1_xonly_pubkey commitments1[2];
-    secp256k1_xonly_pubkey commitments2[2];
-    secp256k1_xonly_pubkey commitments3[2];
-    secp256k1_frost_share shares1[3];
-    secp256k1_frost_share shares2[3];
-    secp256k1_frost_share shares3[3];
-    secp256k1_frost_share agg1, agg2, agg3;
-    secp256k1_frost_share share_buf[3];
-    secp256k1_xonly_pubkey key_buf[3];
-    secp256k1_scalar l1, l2;
+    /* TODO: c.f. musig, example.c */
+    unsigned char pk1[33];
+    unsigned char pk2[33];
+    unsigned char sig[64];
+    unsigned char msg[32];
+    unsigned char id[32];
+    unsigned char sk[32];
+    unsigned char p_sigs[THRESHOLD][32];
+    size_t participants[THRESHOLD];
+    size_t size = 33;
+    secp256k1_scalar privcoeff[N_SIGNERS][THRESHOLD];
+    secp256k1_pubkey pubcoeff[N_SIGNERS][THRESHOLD];
+    secp256k1_pubkey pubkeys[N_SIGNERS];
+    secp256k1_frost_share shares[N_SIGNERS][N_SIGNERS];
+    secp256k1_frost_share agg_shares[N_SIGNERS];
+    secp256k1_scalar l;
     secp256k1_scalar s1, s2;
-    secp256k1_xonly_pubkey combined_pk;
     secp256k1_gej rj;
     secp256k1_ge rp;
+    secp256k1_keypair keypair;
+    secp256k1_frost_secnonce k;
+    secp256k1_frost_keygen_session sessions[N_SIGNERS];
+    int i, j;
 
-    secp256k1_testrand256(sk1);
-    secp256k1_testrand256(sk2);
-    secp256k1_testrand256(sk3);
     /* Round 1.1, 1.2, 1.3, and 1.4 */
-    CHECK(secp256k1_frost_keygen_init(ctx, coefficients1, commitments1, 2, 3, sk1));
-    CHECK(secp256k1_frost_keygen_init(ctx, coefficients2, commitments2, 2, 3, sk2));
-    CHECK(secp256k1_frost_keygen_init(ctx, coefficients3, commitments3, 2, 3, sk3));
+    for (i = 0; i < N_SIGNERS; i++) {
+        secp256k1_testrand256(sk);
+        CHECK(secp256k1_frost_keygen_init(ctx, &sessions[i], privcoeff[i], pubcoeff[i], THRESHOLD, N_SIGNERS, i+1, sk));
+        pubkeys[i] = sessions[i].coeff_pk;
+    }
+    /* Round 2.4 */
+    for (i = 0; i < N_SIGNERS; i++) {
+        CHECK(secp256k1_frost_pubkey_combine(ctx, NULL, &sessions[i], pubkeys));
+    }
     /* Round 2.1 */
-    secp256k1_frost_generate_shares(shares1, coefficients1, 2, 3);
-    secp256k1_frost_generate_shares(shares2, coefficients2, 2, 3);
-    secp256k1_frost_generate_shares(shares3, coefficients3, 2, 3);
+    for (i = 0; i < N_SIGNERS; i++) {
+        secp256k1_frost_generate_shares(shares[i], privcoeff[i], &sessions[i]);
+    }
     /* Round 2.3 */
-    share_buf[0] = shares1[0];
-    share_buf[1] = shares2[0];
-    share_buf[2] = shares3[0];
-    secp256k1_frost_aggregate_shares(&agg1, share_buf, 3);
-    share_buf[0] = shares1[1];
-    share_buf[1] = shares2[1];
-    share_buf[2] = shares3[1];
-    secp256k1_frost_aggregate_shares(&agg2, share_buf, 3);
-    share_buf[0] = shares1[2];
-    share_buf[1] = shares2[2];
-    share_buf[2] = shares3[2];
-    secp256k1_frost_aggregate_shares(&agg3, share_buf, 3);
-    /* Round 2.4 */
-    key_buf[0] = commitments1[0];
-    key_buf[1] = commitments2[0];
-    key_buf[2] = commitments3[0];
-    CHECK(secp256k1_frost_pubkey_combine(ctx, NULL, &combined_pk, key_buf, 3));
+    for (i = 0; i < N_SIGNERS; i++) {
+        secp256k1_frost_share rec_shares[N_SIGNERS];
+
+        for (j = 0; j < N_SIGNERS; j++) {
+            rec_shares[j] = shares[j][sessions[i].my_index - 1];
+        }
+
+        /* TODO: pull participant share from session */
+        secp256k1_frost_aggregate_shares(&agg_shares[i], rec_shares, &sessions[i]);
+    }
 
     /* Reconstruct secret */
-    participants[0] = 1;
-    participants[1] = 2;
-    secp256k1_frost_lagrange_coefficient(&l1, participants, 2, 1);
-    secp256k1_frost_lagrange_coefficient(&l2, participants, 2, 2);
-    secp256k1_scalar_set_b32(&s1, agg1.data, NULL);
-    secp256k1_scalar_set_b32(&s2, agg2.data, NULL);
-    secp256k1_scalar_mul(&s1, &s1, &l1);
-    secp256k1_scalar_mul(&s2, &s2, &l2);
-    secp256k1_scalar_add(&s1, &s1, &s2);
+    for (i = 0; i < THRESHOLD; i++) {
+        participants[i] = sessions[i].my_index;
+    }
+    secp256k1_scalar_clear(&s2);
+    for (i = 0; i < THRESHOLD; i++) {
+        secp256k1_frost_lagrange_coefficient(&l, participants, THRESHOLD, sessions[i].my_index);
+        secp256k1_scalar_set_b32(&s1, agg_shares[i].data, NULL);
+        secp256k1_scalar_mul(&s1, &s1, &l);
+        secp256k1_scalar_add(&s2, &s2, &s1);
+    }
 
     /* Test secret */
-    secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &rj, &s1);
+    secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &rj, &s2);
     secp256k1_ge_set_gej(&rp, &rj);
-    secp256k1_xonly_pubkey_save(&key_buf[0], &rp);
-    CHECK(secp256k1_xonly_pubkey_serialize(ctx, pk1, &key_buf[0]));
-    CHECK(secp256k1_xonly_pubkey_serialize(ctx, pk2, &combined_pk));
-    CHECK(secp256k1_memcmp_var(pk1, pk2, sizeof(pk1)) == 0);
-    secp256k1_scalar_clear(&s2);
-    secp256k1_scalar_add(&s2, &s2, &coefficients1[0]);
-    secp256k1_scalar_add(&s2, &s2, &coefficients2[0]);
-    secp256k1_scalar_add(&s2, &s2, &coefficients3[0]);
+    secp256k1_pubkey_save(&pubkeys[0], &rp);
+    CHECK(secp256k1_ec_pubkey_serialize(ctx, pk1, &size, &pubkeys[0], SECP256K1_EC_COMPRESSED));
+    CHECK(secp256k1_xonly_pubkey_serialize(ctx, pk2, &sessions[0].combined_pk));
+    CHECK(secp256k1_memcmp_var(&pk1[1], pk2, 32) == 0);
+    secp256k1_scalar_clear(&s1);
+    for (i = 0; i < N_SIGNERS; i++) {
+        secp256k1_scalar_add(&s1, &s1, &privcoeff[i][0]);
+    }
     CHECK(secp256k1_scalar_eq(&s1, &s2));
+
+    /* Test signing */
+    secp256k1_testrand256(msg);
+
+    secp256k1_scalar_get_b32(sk, &s1);
+    CHECK(secp256k1_keypair_create(ctx, &keypair, sk));
+    CHECK(secp256k1_schnorrsig_sign(ctx, sig, msg, &keypair, NULL, NULL));
+    CHECK(secp256k1_schnorrsig_verify(ctx, sig, msg, &sessions[0].combined_pk));
+
+    /* Generate nonces */
+    /* TODO: need a noncegen session object */
+    /* TODO: use separate ID for each participant */
+    secp256k1_testrand256(id);
+    for (i = 0; i < THRESHOLD; i++) {
+        secp256k1_nonce_function_frost(&k, id, agg_shares[i].data, msg, pk2, frost_algo, 9, NULL);
+        secp256k1_scalar_set_b32(&s1, k.data, NULL);
+        secp256k1_ecmult_gen(&ctx->ecmult_gen_ctx, &rj, &s1);
+        secp256k1_ge_set_gej(&rp, &rj);
+        secp256k1_pubkey_save(&pubkeys[i], &rp);
+    }
+    sessions[0].n_signers = THRESHOLD;
+    CHECK(secp256k1_frost_pubkey_combine(ctx, NULL, &sessions[0], pubkeys));
+    CHECK(secp256k1_xonly_pubkey_serialize(ctx, pk2, &sessions[0].combined_pk));
+    /* sign */
+    for (i = 0; i < THRESHOLD; i++) {
+        /* compute challenge hash */
+        secp256k1_schnorrsig_challenge(&s2, pk2, msg, &pk1[1]);
+
+        secp256k1_scalar_set_b32(&s1, agg_shares[i].data, NULL);
+        secp256k1_frost_lagrange_coefficient(&l, participants, THRESHOLD, sessions[i].my_index);
+        secp256k1_scalar_mul(&s1, &s1, &l);
+        secp256k1_scalar_mul(&s2, &s2, &s1);
+        CHECK(secp256k1_xonly_pubkey_serialize(ctx, pk2, &sessions[0].combined_pk));
+        secp256k1_nonce_function_frost(&k, id, agg_shares[i].data, msg, &pk1[1], frost_algo, 9, NULL);
+        secp256k1_scalar_set_b32(&s1, k.data, NULL);
+        if (sessions[0].pk_parity) {
+            secp256k1_scalar_negate(&s1, &s1);
+
+        }
+        secp256k1_scalar_add(&s2, &s2, &s1);
+        secp256k1_scalar_get_b32(p_sigs[i], &s2);
+    }
+    /* combine sigs */
+    secp256k1_scalar_clear(&s1);
+    for (i = 0; i < THRESHOLD; i++) {
+        secp256k1_scalar_set_b32(&s2, p_sigs[i], NULL);
+        secp256k1_scalar_add(&s1, &s1, &s2);
+    }
+    secp256k1_scalar_get_b32(&sig[32], &s1);
+    memcpy(&sig[0], pk2, 32);
+
+    CHECK(secp256k1_schnorrsig_verify(ctx, sig, msg, &sessions[1].combined_pk));
 }
 
 #endif /* SECP256K1_MODULE_FROST_TESTS_H */