diff options
Diffstat (limited to 'src/pk/dsa/dsa_sign_hash.c')
| -rw-r--r-- | src/pk/dsa/dsa_sign_hash.c | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/src/pk/dsa/dsa_sign_hash.c b/src/pk/dsa/dsa_sign_hash.c new file mode 100644 index 0000000..48d29a2 --- /dev/null +++ b/src/pk/dsa/dsa_sign_hash.c @@ -0,0 +1,159 @@ +/* LibTomCrypt, modular cryptographic library -- Tom St Denis + * + * LibTomCrypt is a library that provides various cryptographic + * algorithms in a highly modular and flexible manner. + * + * The library is free for all purposes without any express + * guarantee it works. + * + * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org + */ +#include "tomcrypt.h" + +/** + @file dsa_sign_hash.c + DSA implementation, sign a hash, Tom St Denis +*/ + +#ifdef MDSA + +/** + Sign a hash with DSA + @param in The hash to sign + @param inlen The length of the hash to sign + @param r The "r" integer of the signature (caller must initialize with mp_init() first) + @param s The "s" integer of the signature (caller must initialize with mp_init() first) + @param prng An active PRNG state + @param wprng The index of the PRNG desired + @param key A private DSA key + @return CRYPT_OK if successful +*/ +int dsa_sign_hash_raw(const unsigned char *in, unsigned long inlen, + mp_int *r, mp_int *s, + prng_state *prng, int wprng, dsa_key *key) +{ + mp_int k, kinv, tmp; + unsigned char *buf; + int err; + + LTC_ARGCHK(in != NULL); + LTC_ARGCHK(r != NULL); + LTC_ARGCHK(s != NULL); + LTC_ARGCHK(key != NULL); + + if ((err = prng_is_valid(wprng)) != CRYPT_OK) { + return err; + } + if (key->type != PK_PRIVATE) { + return CRYPT_PK_NOT_PRIVATE; + } + + /* check group order size */ + if (key->qord >= MDSA_MAX_GROUP) { + return CRYPT_INVALID_ARG; + } + + buf = XMALLOC(MDSA_MAX_GROUP); + if (buf == NULL) { + return CRYPT_MEM; + } + + /* Init our temps */ + if ((err = mp_init_multi(&k, &kinv, &tmp, NULL)) != MP_OKAY) { goto error; } + +retry: + + do { + /* gen random k */ + if (prng_descriptor[wprng].read(buf, key->qord, prng) != (unsigned long)key->qord) { + err = CRYPT_ERROR_READPRNG; + goto LBL_ERR; + } + + /* read k */ + if ((err = mp_read_unsigned_bin(&k, buf, key->qord)) != MP_OKAY) { goto error; } + + /* k > 1 ? */ + if (mp_cmp_d(&k, 1) != MP_GT) { goto retry; } + + /* test gcd */ + if ((err = mp_gcd(&k, &key->q, &tmp)) != MP_OKAY) { goto error; } + } while (mp_cmp_d(&tmp, 1) != MP_EQ); + + /* now find 1/k mod q */ + if ((err = mp_invmod(&k, &key->q, &kinv)) != MP_OKAY) { goto error; } + + /* now find r = g^k mod p mod q */ + if ((err = mp_exptmod(&key->g, &k, &key->p, r)) != MP_OKAY) { goto error; } + if ((err = mp_mod(r, &key->q, r)) != MP_OKAY) { goto error; } + + if (mp_iszero(r) == MP_YES) { goto retry; } + + /* now find s = (in + xr)/k mod q */ + if ((err = mp_read_unsigned_bin(&tmp, (unsigned char *)in, inlen)) != MP_OKAY) { goto error; } + if ((err = mp_mul(&key->x, r, s)) != MP_OKAY) { goto error; } + if ((err = mp_add(s, &tmp, s)) != MP_OKAY) { goto error; } + if ((err = mp_mulmod(s, &kinv, &key->q, s)) != MP_OKAY) { goto error; } + + if (mp_iszero(s) == MP_YES) { goto retry; } + + err = CRYPT_OK; + goto LBL_ERR; + +error: + err = mpi_to_ltc_error(err); +LBL_ERR: + mp_clear_multi(&k, &kinv, &tmp, NULL); +#ifdef LTC_CLEAN_STACK + zeromem(buf, MDSA_MAX_GROUP); +#endif + XFREE(buf); + return err; +} + +/** + Sign a hash with DSA + @param in The hash to sign + @param inlen The length of the hash to sign + @param out [out] Where to store the signature + @param outlen [in/out] The max size and resulting size of the signature + @param prng An active PRNG state + @param wprng The index of the PRNG desired + @param key A private DSA key + @return CRYPT_OK if successful +*/ +int dsa_sign_hash(const unsigned char *in, unsigned long inlen, + unsigned char *out, unsigned long *outlen, + prng_state *prng, int wprng, dsa_key *key) +{ + mp_int r, s; + int err; + + LTC_ARGCHK(in != NULL); + LTC_ARGCHK(out != NULL); + LTC_ARGCHK(outlen != NULL); + LTC_ARGCHK(key != NULL); + + if (mp_init_multi(&r, &s, NULL) != MP_OKAY) { + return CRYPT_MEM; + } + + if ((err = dsa_sign_hash_raw(in, inlen, &r, &s, prng, wprng, key)) != CRYPT_OK) { + goto LBL_ERR; + } + + err = der_encode_sequence_multi(out, outlen, + LTC_ASN1_INTEGER, 1UL, &r, + LTC_ASN1_INTEGER, 1UL, &s, + LTC_ASN1_EOL, 0UL, NULL); + +LBL_ERR: + mp_clear_multi(&r, &s, NULL); + return err; +} + +#endif + +/* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_sign_hash.c,v $ */ +/* $Revision: 1.6 $ */ +/* $Date: 2005/05/15 21:48:59 $ */ |