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, tomstdenis (at) gmail.com, http://libtomcrypt.com 10 */ 11 #include "tomcrypt.h" 12 13 /** 14 @file dsa_sign_hash.c 15 DSA implementation, sign a hash, Tom St Denis 16 */ 17 18 #ifdef MDSA 19 20 /** 21 Sign a hash with DSA 22 @param in The hash to sign 23 @param inlen The length of the hash to sign 24 @param r The "r" integer of the signature (caller must initialize with mp_init() first) 25 @param s The "s" integer of the signature (caller must initialize with mp_init() first) 26 @param prng An active PRNG state 27 @param wprng The index of the PRNG desired 28 @param key A private DSA key 29 @return CRYPT_OK if successful 30 */ 31 int dsa_sign_hash_raw(const unsigned char *in, unsigned long inlen, 32 void *r, void *s, 33 prng_state *prng, int wprng, dsa_key *key) 34 { 35 void *k, *kinv, *tmp; 36 unsigned char *buf; 37 int err; 38 39 LTC_ARGCHK(in != NULL); 40 LTC_ARGCHK(r != NULL); 41 LTC_ARGCHK(s != NULL); 42 LTC_ARGCHK(key != NULL); 43 44 if ((err = prng_is_valid(wprng)) != CRYPT_OK) { 45 return err; 46 } 47 if (key->type != PK_PRIVATE) { 48 return CRYPT_PK_NOT_PRIVATE; 49 } 50 51 /* check group order size */ 52 if (key->qord >= MDSA_MAX_GROUP) { 53 return CRYPT_INVALID_ARG; 54 } 55 56 buf = XMALLOC(MDSA_MAX_GROUP); 57 if (buf == NULL) { 58 return CRYPT_MEM; 59 } 60 61 /* Init our temps */ 62 if ((err = mp_init_multi(&k, &kinv, &tmp, NULL)) != CRYPT_OK) { goto ERRBUF; } 63 64 retry: 65 66 do { 67 /* gen random k */ 68 if (prng_descriptor[wprng].read(buf, key->qord, prng) != (unsigned long)key->qord) { 69 err = CRYPT_ERROR_READPRNG; 70 goto error; 71 } 72 73 /* read k */ 74 if ((err = mp_read_unsigned_bin(k, buf, key->qord)) != CRYPT_OK) { goto error; } 75 76 /* k > 1 ? */ 77 if (mp_cmp_d(k, 1) != LTC_MP_GT) { goto retry; } 78 79 /* test gcd */ 80 if ((err = mp_gcd(k, key->q, tmp)) != CRYPT_OK) { goto error; } 81 } while (mp_cmp_d(tmp, 1) != LTC_MP_EQ); 82 83 /* now find 1/k mod q */ 84 if ((err = mp_invmod(k, key->q, kinv)) != CRYPT_OK) { goto error; } 85 86 /* now find r = g^k mod p mod q */ 87 if ((err = mp_exptmod(key->g, k, key->p, r)) != CRYPT_OK) { goto error; } 88 if ((err = mp_mod(r, key->q, r)) != CRYPT_OK) { goto error; } 89 90 if (mp_iszero(r) == LTC_MP_YES) { goto retry; } 91 92 /* now find s = (in + xr)/k mod q */ 93 if ((err = mp_read_unsigned_bin(tmp, (unsigned char *)in, inlen)) != CRYPT_OK) { goto error; } 94 if ((err = mp_mul(key->x, r, s)) != CRYPT_OK) { goto error; } 95 if ((err = mp_add(s, tmp, s)) != CRYPT_OK) { goto error; } 96 if ((err = mp_mulmod(s, kinv, key->q, s)) != CRYPT_OK) { goto error; } 97 98 if (mp_iszero(s) == LTC_MP_YES) { goto retry; } 99 100 err = CRYPT_OK; 101 error: 102 mp_clear_multi(k, kinv, tmp, NULL); 103 ERRBUF: 104 #ifdef LTC_CLEAN_STACK 105 zeromem(buf, MDSA_MAX_GROUP); 106 #endif 107 XFREE(buf); 108 return err; 109 } 110 111 /** 112 Sign a hash with DSA 113 @param in The hash to sign 114 @param inlen The length of the hash to sign 115 @param out [out] Where to store the signature 116 @param outlen [in/out] The max size and resulting size of the signature 117 @param prng An active PRNG state 118 @param wprng The index of the PRNG desired 119 @param key A private DSA key 120 @return CRYPT_OK if successful 121 */ 122 int dsa_sign_hash(const unsigned char *in, unsigned long inlen, 123 unsigned char *out, unsigned long *outlen, 124 prng_state *prng, int wprng, dsa_key *key) 125 { 126 void *r, *s; 127 int err; 128 129 LTC_ARGCHK(in != NULL); 130 LTC_ARGCHK(out != NULL); 131 LTC_ARGCHK(outlen != NULL); 132 LTC_ARGCHK(key != NULL); 133 134 if (mp_init_multi(&r, &s, NULL) != CRYPT_OK) { 135 return CRYPT_MEM; 136 } 137 138 if ((err = dsa_sign_hash_raw(in, inlen, r, s, prng, wprng, key)) != CRYPT_OK) { 139 goto error; 140 } 141 142 err = der_encode_sequence_multi(out, outlen, 143 LTC_ASN1_INTEGER, 1UL, r, 144 LTC_ASN1_INTEGER, 1UL, s, 145 LTC_ASN1_EOL, 0UL, NULL); 146 147 error: 148 mp_clear_multi(r, s, NULL); 149 return err; 150 } 151 152 #endif 153 154 /* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_sign_hash.c,v $ */ 155 /* $Revision: 1.12 $ */ 156 /* $Date: 2006/12/04 22:27:56 $ */ 157
