1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
3 * LibTomCrypt is a library that provides various cryptographic
4 * algorithms in a highly modular and flexible manner.
6 * The library is free for all purposes without any express
15 @file ecc_verify_hash.c
16 ECC Crypto, Tom St Denis
19 static int _ecc_verify_hash(const unsigned char *sig, unsigned long siglen,
20 const unsigned char *hash, unsigned long hashlen,
21 int *stat, ecc_key *key, int sigformat)
24 void *r, *s, *v, *w, *u1, *u2, *e, *p, *m;
27 unsigned long pbits, pbytes, i, shift_right;
28 unsigned char ch, buf[MAXBLOCKSIZE];
30 LTC_ARGCHK(sig != NULL);
31 LTC_ARGCHK(hash != NULL);
32 LTC_ARGCHK(stat != NULL);
33 LTC_ARGCHK(key != NULL);
35 /* default to invalid signature */
39 /* is the IDX valid ? */
40 if (ltc_ecc_is_valid_idx(key->idx) != 1) {
41 return CRYPT_PK_INVALID_TYPE;
45 if ((err = mp_init_multi(&r, &s, &v, &w, &u1, &u2, &p, &e, &m, NULL)) != CRYPT_OK) {
50 mG = ltc_ecc_new_point();
51 mQ = ltc_ecc_new_point();
52 if (mQ == NULL || mG == NULL) {
59 if ((siglen % 2) == 1) {
60 err = CRYPT_INVALID_PACKET;
64 if ((err = mp_read_unsigned_bin(r, (unsigned char *)sig, i)) != CRYPT_OK) { goto error; }
65 if ((err = mp_read_unsigned_bin(s, (unsigned char *)sig+i, i)) != CRYPT_OK) { goto error; }
69 if ((err = der_decode_sequence_multi(sig, siglen,
70 LTC_ASN1_INTEGER, 1UL, r,
71 LTC_ASN1_INTEGER, 1UL, s,
72 LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) { goto error; }
76 if ((err = mp_read_radix(p, (char *)key->dp->order, 16)) != CRYPT_OK) { goto error; }
79 if ((err = mp_read_radix(m, (char *)key->dp->prime, 16)) != CRYPT_OK) { goto error; }
82 if (mp_iszero(r) || mp_iszero(s) || mp_cmp(r, p) != LTC_MP_LT || mp_cmp(s, p) != LTC_MP_LT) {
83 err = CRYPT_INVALID_PACKET;
87 /* read hash - truncate if needed */
88 pbits = mp_count_bits(p);
89 pbytes = (pbits+7) >> 3;
90 if (pbits > hashlen*8) {
91 if ((err = mp_read_unsigned_bin(e, (unsigned char *)hash, hashlen)) != CRYPT_OK) { goto error; }
93 else if (pbits % 8 == 0) {
94 if ((err = mp_read_unsigned_bin(e, (unsigned char *)hash, pbytes)) != CRYPT_OK) { goto error; }
97 shift_right = 8 - pbits % 8;
98 for (i=0, ch=0; i<pbytes; i++) {
100 ch = (hash[i] << (8-shift_right));
101 buf[i] = buf[i] ^ (hash[i] >> shift_right);
103 if ((err = mp_read_unsigned_bin(e, (unsigned char *)buf, pbytes)) != CRYPT_OK) { goto error; }
107 if ((err = mp_invmod(s, p, w)) != CRYPT_OK) { goto error; }
110 if ((err = mp_mulmod(e, w, p, u1)) != CRYPT_OK) { goto error; }
113 if ((err = mp_mulmod(r, w, p, u2)) != CRYPT_OK) { goto error; }
116 if ((err = mp_read_radix(mG->x, (char *)key->dp->Gx, 16)) != CRYPT_OK) { goto error; }
117 if ((err = mp_read_radix(mG->y, (char *)key->dp->Gy, 16)) != CRYPT_OK) { goto error; }
118 if ((err = mp_set(mG->z, 1)) != CRYPT_OK) { goto error; }
120 if ((err = mp_copy(key->pubkey.x, mQ->x)) != CRYPT_OK) { goto error; }
121 if ((err = mp_copy(key->pubkey.y, mQ->y)) != CRYPT_OK) { goto error; }
122 if ((err = mp_copy(key->pubkey.z, mQ->z)) != CRYPT_OK) { goto error; }
124 /* compute u1*mG + u2*mQ = mG */
125 if (ltc_mp.ecc_mul2add == NULL) {
126 if ((err = ltc_mp.ecc_ptmul(u1, mG, mG, m, 0)) != CRYPT_OK) { goto error; }
127 if ((err = ltc_mp.ecc_ptmul(u2, mQ, mQ, m, 0)) != CRYPT_OK) { goto error; }
129 /* find the montgomery mp */
130 if ((err = mp_montgomery_setup(m, &mp)) != CRYPT_OK) { goto error; }
133 if ((err = ltc_mp.ecc_ptadd(mQ, mG, mG, m, mp)) != CRYPT_OK) { goto error; }
136 if ((err = ltc_mp.ecc_map(mG, m, mp)) != CRYPT_OK) { goto error; }
138 /* use Shamir's trick to compute u1*mG + u2*mQ using half of the doubles */
139 if ((err = ltc_mp.ecc_mul2add(mG, u1, mQ, u2, mG, m)) != CRYPT_OK) { goto error; }
143 if ((err = mp_mod(mG->x, p, v)) != CRYPT_OK) { goto error; }
146 if (mp_cmp(v, r) == LTC_MP_EQ) {
150 /* clear up and return */
153 ltc_ecc_del_point(mG);
154 ltc_ecc_del_point(mQ);
155 mp_clear_multi(r, s, v, w, u1, u2, p, e, m, NULL);
157 mp_montgomery_free(mp);
163 Verify an ECC signature
164 @param sig The signature to verify
165 @param siglen The length of the signature (octets)
166 @param hash The hash (message digest) that was signed
167 @param hashlen The length of the hash (octets)
168 @param stat Result of signature, 1==valid, 0==invalid
169 @param key The corresponding public ECC key
170 @return CRYPT_OK if successful (even if the signature is not valid)
172 int ecc_verify_hash(const unsigned char *sig, unsigned long siglen,
173 const unsigned char *hash, unsigned long hashlen,
174 int *stat, ecc_key *key)
176 return _ecc_verify_hash(sig, siglen, hash, hashlen, stat, key, 0);
180 Verify an ECC signature in RFC7518 format
181 @param sig The signature to verify
182 @param siglen The length of the signature (octets)
183 @param hash The hash (message digest) that was signed
184 @param hashlen The length of the hash (octets)
185 @param stat Result of signature, 1==valid, 0==invalid
186 @param key The corresponding public ECC key
187 @return CRYPT_OK if successful (even if the signature is not valid)
189 int ecc_verify_hash_rfc7518(const unsigned char *sig, unsigned long siglen,
190 const unsigned char *hash, unsigned long hashlen,
191 int *stat, ecc_key *key)
193 return _ecc_verify_hash(sig, siglen, hash, hashlen, stat, key, 1);
198 /* ref: $Format:%D$ */
199 /* git commit: $Format:%H$ */
200 /* commit time: $Format:%ai$ */