Mercurial > dropbear
view libtomcrypt/src/pk/dsa/dsa_verify_hash.c @ 758:1c607a62d235 ecc
Set LTC_SOURCE for proper ltm_desc etc
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Fri, 29 Mar 2013 00:26:46 +0800 (2013-03-28) |
parents | 0cbe8f6dbf9e |
children | f849a5ca2efc |
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/* 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.com */ #include "tomcrypt.h" /** @file dsa_verify_hash.c DSA implementation, verify a signature, Tom St Denis */ #ifdef MDSA /** Verify a DSA signature @param r DSA "r" parameter @param s DSA "s" parameter @param hash The hash that was signed @param hashlen The length of the hash that was signed @param stat [out] The result of the signature verification, 1==valid, 0==invalid @param key The corresponding public DH key @return CRYPT_OK if successful (even if the signature is invalid) */ int dsa_verify_hash_raw( void *r, void *s, const unsigned char *hash, unsigned long hashlen, int *stat, dsa_key *key) { void *w, *v, *u1, *u2; int err; LTC_ARGCHK(r != NULL); LTC_ARGCHK(s != NULL); LTC_ARGCHK(stat != NULL); LTC_ARGCHK(key != NULL); /* default to invalid signature */ *stat = 0; /* init our variables */ if ((err = mp_init_multi(&w, &v, &u1, &u2, NULL)) != CRYPT_OK) { return err; } /* neither r or s can be null or >q*/ if (mp_iszero(r) == LTC_MP_YES || mp_iszero(s) == LTC_MP_YES || mp_cmp(r, key->q) != LTC_MP_LT || mp_cmp(s, key->q) != LTC_MP_LT) { err = CRYPT_INVALID_PACKET; goto error; } /* w = 1/s mod q */ if ((err = mp_invmod(s, key->q, w)) != CRYPT_OK) { goto error; } /* u1 = m * w mod q */ if ((err = mp_read_unsigned_bin(u1, (unsigned char *)hash, hashlen)) != CRYPT_OK) { goto error; } if ((err = mp_mulmod(u1, w, key->q, u1)) != CRYPT_OK) { goto error; } /* u2 = r*w mod q */ if ((err = mp_mulmod(r, w, key->q, u2)) != CRYPT_OK) { goto error; } /* v = g^u1 * y^u2 mod p mod q */ if ((err = mp_exptmod(key->g, u1, key->p, u1)) != CRYPT_OK) { goto error; } if ((err = mp_exptmod(key->y, u2, key->p, u2)) != CRYPT_OK) { goto error; } if ((err = mp_mulmod(u1, u2, key->p, v)) != CRYPT_OK) { goto error; } if ((err = mp_mod(v, key->q, v)) != CRYPT_OK) { goto error; } /* if r = v then we're set */ if (mp_cmp(r, v) == LTC_MP_EQ) { *stat = 1; } err = CRYPT_OK; error: mp_clear_multi(w, v, u1, u2, NULL); return err; } /** Verify a DSA signature @param sig The signature @param siglen The length of the signature (octets) @param hash The hash that was signed @param hashlen The length of the hash that was signed @param stat [out] The result of the signature verification, 1==valid, 0==invalid @param key The corresponding public DH key @return CRYPT_OK if successful (even if the signature is invalid) */ int dsa_verify_hash(const unsigned char *sig, unsigned long siglen, const unsigned char *hash, unsigned long hashlen, int *stat, dsa_key *key) { int err; void *r, *s; if ((err = mp_init_multi(&r, &s, NULL)) != CRYPT_OK) { return CRYPT_MEM; } /* decode the sequence */ if ((err = der_decode_sequence_multi(sig, siglen, LTC_ASN1_INTEGER, 1UL, r, LTC_ASN1_INTEGER, 1UL, s, LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) { goto LBL_ERR; } /* do the op */ err = dsa_verify_hash_raw(r, s, hash, hashlen, stat, key); LBL_ERR: mp_clear_multi(r, s, NULL); return err; } #endif /* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_verify_hash.c,v $ */ /* $Revision: 1.13 $ */ /* $Date: 2006/12/04 03:18:43 $ */