Mercurial > dropbear
diff rsa_exptmod.c @ 143:5d99163f7e32 libtomcrypt-orig
import of libtomcrypt 0.99
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Sun, 19 Dec 2004 11:34:45 +0000 |
parents | 6362d3854bb4 |
children |
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--- a/rsa_exptmod.c Tue Jun 15 14:07:21 2004 +0000 +++ b/rsa_exptmod.c Sun Dec 19 11:34:45 2004 +0000 @@ -14,6 +14,7 @@ #ifdef MRSA +/* compute an RSA modular exponentiation */ int rsa_exptmod(const unsigned char *in, unsigned long inlen, unsigned char *out, unsigned long *outlen, int which, prng_state *prng, int prng_idx, @@ -28,11 +29,13 @@ _ARGCHK(outlen != NULL); _ARGCHK(key != NULL); + /* valid prng? */ if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) { return err; } - if (which == PK_PRIVATE && (key->type != PK_PRIVATE && key->type != PK_PRIVATE_OPTIMIZED)) { + /* is the key of the right type for the operation? */ + if (which == PK_PRIVATE && (key->type != PK_PRIVATE)) { return CRYPT_PK_NOT_PRIVATE; } @@ -42,7 +45,7 @@ } /* init and copy into tmp */ - if ((err = mp_init_multi(&tmp, &tmpa, &tmpb, NULL)) != MP_OKAY) { goto error; } + if ((err = mp_init_multi(&tmp, &tmpa, &tmpb, NULL)) != MP_OKAY) { return mpi_to_ltc_error(err); } if ((err = mp_read_unsigned_bin(&tmp, (unsigned char *)in, (int)inlen)) != MP_OKAY) { goto error; } /* sanity check on the input */ @@ -52,24 +55,23 @@ } /* are we using the private exponent and is the key optimized? */ - if (which == PK_PRIVATE && key->type == PK_PRIVATE_OPTIMIZED) { + if (which == PK_PRIVATE) { /* tmpa = tmp^dP mod p */ if ((err = tim_exptmod(prng, prng_idx, &tmp, &key->e, &key->dP, &key->p, &tmpa)) != MP_OKAY) { goto error; } /* tmpb = tmp^dQ mod q */ if ((err = tim_exptmod(prng, prng_idx, &tmp, &key->e, &key->dQ, &key->q, &tmpb)) != MP_OKAY) { goto error; } - /* tmp = tmpa*qP + tmpb*pQ mod N */ - if ((err = mp_mul(&tmpa, &key->qP, &tmpa)) != MP_OKAY) { goto error; } - if ((err = mp_mul(&tmpb, &key->pQ, &tmpb)) != MP_OKAY) { goto error; } - if ((err = mp_addmod(&tmpa, &tmpb, &key->N, &tmp)) != MP_OKAY) { goto error; } + /* tmp = (tmpa - tmpb) * qInv (mod p) */ + if ((err = mp_sub(&tmpa, &tmpb, &tmp)) != MP_OKAY) { goto error; } + if ((err = mp_mulmod(&tmp, &key->qP, &key->p, &tmp)) != MP_OKAY) { goto error; } + + /* tmp = tmpb + q * tmp */ + if ((err = mp_mul(&tmp, &key->q, &tmp)) != MP_OKAY) { goto error; } + if ((err = mp_add(&tmp, &tmpb, &tmp)) != MP_OKAY) { goto error; } } else { /* exptmod it */ - if (which == PK_PRIVATE) { - if ((err = tim_exptmod(prng, prng_idx, &tmp, &key->e, &key->d, &key->N, &tmp)) != MP_OKAY) { goto error; } - } else { - if ((err = mp_exptmod(&tmp, &key->e, &key->N, &tmp)) != MP_OKAY) { goto error; } - } + if ((err = mp_exptmod(&tmp, &key->e, &key->N, &tmp)) != MP_OKAY) { goto error; } } /* read it back */