Mercurial > dropbear
view dsa_sign_hash.c @ 18:712dd6dfb0eb libtomcrypt
makefile
author | Matt Johnston <matt@ucc.asn.au> |
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date | Tue, 15 Jun 2004 14:34:07 +0000 |
parents | d7da3b1e1540 |
children | 5d99163f7e32 |
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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, [email protected], http://libtomcrypt.org */ #include "mycrypt.h" #ifdef MDSA 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 k, kinv, tmp, r, s; unsigned char buf[512]; int err, y; unsigned long len; _ARGCHK(in != NULL); _ARGCHK(out != NULL); _ARGCHK(outlen != NULL); _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 >= (int)sizeof(buf)) { return CRYPT_INVALID_ARG; } /* Init our temps */ if ((err = mp_init_multi(&k, &kinv, &r, &s, &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 done; } /* 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; } /* now store em both */ /* first check that we have enough room */ if (*outlen < (unsigned long)(PACKET_SIZE + 4 + mp_unsigned_bin_size(&s) + mp_unsigned_bin_size(&r))) { err = CRYPT_BUFFER_OVERFLOW; goto done; } /* packet header */ packet_store_header(out, PACKET_SECT_DSA, PACKET_SUB_SIGNED); y = PACKET_SIZE; /* store length of r */ len = mp_unsigned_bin_size(&r); out[y++] = (len>>8)&255; out[y++] = len&255; /* store r */ if ((err = mp_to_unsigned_bin(&r, out+y)) != MP_OKAY) { goto error; } y += len; /* store length of s */ len = mp_unsigned_bin_size(&s); out[y++] = (len>>8)&255; out[y++] = len&255; /* store s */ if ((err = mp_to_unsigned_bin(&s, out+y)) != MP_OKAY) { goto error; } y += len; /* reset size */ *outlen = y; err = CRYPT_OK; goto done; error : err = mpi_to_ltc_error(err); done : mp_clear_multi(&k, &kinv, &r, &s, &tmp, NULL); #ifdef CLEAN_STACK zeromem(buf, sizeof(buf)); #endif return err; } #endif