Mercurial > dropbear
comparison libtomcrypt/src/pk/ecc/ecc_verify_hash.c @ 382:0cbe8f6dbf9e
propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head 2af22fb4e878750b88f80f90d439b316d229796f)
to branch 'au.asn.ucc.matt.dropbear' (head 02c413252c90e9de8e03d91e9939dde3029f5c0a)
author | Matt Johnston <matt@ucc.asn.au> |
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date | Thu, 11 Jan 2007 02:41:05 +0000 |
parents | |
children | ac2158e3e403 |
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379:b66a00272a90 | 382:0cbe8f6dbf9e |
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis | |
2 * | |
3 * LibTomCrypt is a library that provides various cryptographic | |
4 * algorithms in a highly modular and flexible manner. | |
5 * | |
6 * The library is free for all purposes without any express | |
7 * guarantee it works. | |
8 * | |
9 * Tom St Denis, [email protected], http://libtomcrypt.com | |
10 */ | |
11 | |
12 /* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b | |
13 * | |
14 * All curves taken from NIST recommendation paper of July 1999 | |
15 * Available at http://csrc.nist.gov/cryptval/dss.htm | |
16 */ | |
17 #include "tomcrypt.h" | |
18 | |
19 /** | |
20 @file ecc_verify_hash.c | |
21 ECC Crypto, Tom St Denis | |
22 */ | |
23 | |
24 #ifdef MECC | |
25 | |
26 /* verify | |
27 * | |
28 * w = s^-1 mod n | |
29 * u1 = xw | |
30 * u2 = rw | |
31 * X = u1*G + u2*Q | |
32 * v = X_x1 mod n | |
33 * accept if v == r | |
34 */ | |
35 | |
36 /** | |
37 Verify an ECC signature | |
38 @param sig The signature to verify | |
39 @param siglen The length of the signature (octets) | |
40 @param hash The hash (message digest) that was signed | |
41 @param hashlen The length of the hash (octets) | |
42 @param stat Result of signature, 1==valid, 0==invalid | |
43 @param key The corresponding public ECC key | |
44 @return CRYPT_OK if successful (even if the signature is not valid) | |
45 */ | |
46 int ecc_verify_hash(const unsigned char *sig, unsigned long siglen, | |
47 const unsigned char *hash, unsigned long hashlen, | |
48 int *stat, ecc_key *key) | |
49 { | |
50 ecc_point *mG, *mQ; | |
51 void *r, *s, *v, *w, *u1, *u2, *e, *p, *m; | |
52 void *mp; | |
53 int err; | |
54 | |
55 LTC_ARGCHK(sig != NULL); | |
56 LTC_ARGCHK(hash != NULL); | |
57 LTC_ARGCHK(stat != NULL); | |
58 LTC_ARGCHK(key != NULL); | |
59 | |
60 /* default to invalid signature */ | |
61 *stat = 0; | |
62 mp = NULL; | |
63 | |
64 /* is the IDX valid ? */ | |
65 if (ltc_ecc_is_valid_idx(key->idx) != 1) { | |
66 return CRYPT_PK_INVALID_TYPE; | |
67 } | |
68 | |
69 /* allocate ints */ | |
70 if ((err = mp_init_multi(&r, &s, &v, &w, &u1, &u2, &p, &e, &m, NULL)) != CRYPT_OK) { | |
71 return CRYPT_MEM; | |
72 } | |
73 | |
74 /* allocate points */ | |
75 mG = ltc_ecc_new_point(); | |
76 mQ = ltc_ecc_new_point(); | |
77 if (mQ == NULL || mG == NULL) { | |
78 err = CRYPT_MEM; | |
79 goto error; | |
80 } | |
81 | |
82 /* parse header */ | |
83 if ((err = der_decode_sequence_multi(sig, siglen, | |
84 LTC_ASN1_INTEGER, 1UL, r, | |
85 LTC_ASN1_INTEGER, 1UL, s, | |
86 LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) { | |
87 goto error; | |
88 } | |
89 | |
90 /* get the order */ | |
91 if ((err = mp_read_radix(p, (char *)key->dp->order, 16)) != CRYPT_OK) { goto error; } | |
92 | |
93 /* get the modulus */ | |
94 if ((err = mp_read_radix(m, (char *)key->dp->prime, 16)) != CRYPT_OK) { goto error; } | |
95 | |
96 /* check for zero */ | |
97 if (mp_iszero(r) || mp_iszero(s) || mp_cmp(r, p) != LTC_MP_LT || mp_cmp(s, p) != LTC_MP_LT) { | |
98 err = CRYPT_INVALID_PACKET; | |
99 goto error; | |
100 } | |
101 | |
102 /* read hash */ | |
103 if ((err = mp_read_unsigned_bin(e, (unsigned char *)hash, (int)hashlen)) != CRYPT_OK) { goto error; } | |
104 | |
105 /* w = s^-1 mod n */ | |
106 if ((err = mp_invmod(s, p, w)) != CRYPT_OK) { goto error; } | |
107 | |
108 /* u1 = ew */ | |
109 if ((err = mp_mulmod(e, w, p, u1)) != CRYPT_OK) { goto error; } | |
110 | |
111 /* u2 = rw */ | |
112 if ((err = mp_mulmod(r, w, p, u2)) != CRYPT_OK) { goto error; } | |
113 | |
114 /* find mG and mQ */ | |
115 if ((err = mp_read_radix(mG->x, (char *)key->dp->Gx, 16)) != CRYPT_OK) { goto error; } | |
116 if ((err = mp_read_radix(mG->y, (char *)key->dp->Gy, 16)) != CRYPT_OK) { goto error; } | |
117 if ((err = mp_set(mG->z, 1)) != CRYPT_OK) { goto error; } | |
118 | |
119 if ((err = mp_copy(key->pubkey.x, mQ->x)) != CRYPT_OK) { goto error; } | |
120 if ((err = mp_copy(key->pubkey.y, mQ->y)) != CRYPT_OK) { goto error; } | |
121 if ((err = mp_copy(key->pubkey.z, mQ->z)) != CRYPT_OK) { goto error; } | |
122 | |
123 /* compute u1*mG + u2*mQ = mG */ | |
124 if (ltc_mp.ecc_mul2add == NULL) { | |
125 if ((err = ltc_mp.ecc_ptmul(u1, mG, mG, m, 0)) != CRYPT_OK) { goto error; } | |
126 if ((err = ltc_mp.ecc_ptmul(u2, mQ, mQ, m, 0)) != CRYPT_OK) { goto error; } | |
127 | |
128 /* find the montgomery mp */ | |
129 if ((err = mp_montgomery_setup(m, &mp)) != CRYPT_OK) { goto error; } | |
130 | |
131 /* add them */ | |
132 if ((err = ltc_mp.ecc_ptadd(mQ, mG, mG, m, mp)) != CRYPT_OK) { goto error; } | |
133 | |
134 /* reduce */ | |
135 if ((err = ltc_mp.ecc_map(mG, m, mp)) != CRYPT_OK) { goto error; } | |
136 } else { | |
137 /* use Shamir's trick to compute u1*mG + u2*mQ using half of the doubles */ | |
138 if ((err = ltc_mp.ecc_mul2add(mG, u1, mQ, u2, mG, m)) != CRYPT_OK) { goto error; } | |
139 } | |
140 | |
141 /* v = X_x1 mod n */ | |
142 if ((err = mp_mod(mG->x, p, v)) != CRYPT_OK) { goto error; } | |
143 | |
144 /* does v == r */ | |
145 if (mp_cmp(v, r) == LTC_MP_EQ) { | |
146 *stat = 1; | |
147 } | |
148 | |
149 /* clear up and return */ | |
150 err = CRYPT_OK; | |
151 error: | |
152 ltc_ecc_del_point(mG); | |
153 ltc_ecc_del_point(mQ); | |
154 mp_clear_multi(r, s, v, w, u1, u2, p, e, m, NULL); | |
155 if (mp != NULL) { | |
156 mp_montgomery_free(mp); | |
157 } | |
158 return err; | |
159 } | |
160 | |
161 #endif | |
162 /* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_verify_hash.c,v $ */ | |
163 /* $Revision: 1.12 $ */ | |
164 /* $Date: 2006/12/04 05:07:59 $ */ | |
165 |