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RSA in case CRT optimization parameters are not populated

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rsa_exptmod(), ran on the private key, makes use of CRT optimization
parameters. In some use-cases, the given key does not include the
optimization parameters.

This patch allows rsa_exptmod() to run without the CRT parameters,
using directly mp_exptmod().

Signed-off-by: Pascal Brand <pascal.brand@st.com>
This commit is contained in:
Pascal Brand 2014-09-18 02:12:59 +02:00 committed by Steffen Jaeckel
parent cb2322f8de
commit 2bb3f0246f
1 changed files with 23 additions and 10 deletions
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33
src/pk/rsa/rsa_exptmod.c
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@ -100,19 +100,32 @@ int rsa_exptmod(const unsigned char *in, unsigned long inlen,
}
#endif /* LTC_RSA_BLINDING */
/* tmpa = tmp^dP mod p */
if ((err = mp_exptmod(tmp, key->dP, key->p, tmpa)) != CRYPT_OK) { goto error; }
if (key->dP == NULL) {
/*
* In case CRT optimization parameters are provided,
* the private key is directly used
*/
LTC_ARGCHK(key->dQ == NULL);
LTC_ARGCHK(key->qP == NULL);
LTC_ARGCHK(key->p == NULL);
LTC_ARGCHK(key->q == NULL);
/* exptmod it */
if ((err = mp_exptmod(tmp, key->d, key->N, tmp)) != CRYPT_OK) { goto error; }
} else {
/* tmpa = tmp^dP mod p */
if ((err = mp_exptmod(tmp, key->dP, key->p, tmpa)) != CRYPT_OK) { goto error; }
/* tmpb = tmp^dQ mod q */
if ((err = mp_exptmod(tmp, key->dQ, key->q, tmpb)) != CRYPT_OK) { goto error; }
/* tmpb = tmp^dQ mod q */
if ((err = mp_exptmod(tmp, key->dQ, key->q, tmpb)) != CRYPT_OK) { goto error; }
/* tmp = (tmpa - tmpb) * qInv (mod p) */
if ((err = mp_sub(tmpa, tmpb, tmp)) != CRYPT_OK) { goto error; }
if ((err = mp_mulmod(tmp, key->qP, key->p, tmp)) != CRYPT_OK) { goto error; }
/* tmp = (tmpa - tmpb) * qInv (mod p) */
if ((err = mp_sub(tmpa, tmpb, tmp)) != CRYPT_OK) { goto error; }
if ((err = mp_mulmod(tmp, key->qP, key->p, tmp)) != CRYPT_OK) { goto error; }
/* tmp = tmpb + q * tmp */
if ((err = mp_mul(tmp, key->q, tmp)) != CRYPT_OK) { goto error; }
if ((err = mp_add(tmp, tmpb, tmp)) != CRYPT_OK) { goto error; }
/* tmp = tmpb + q * tmp */
if ((err = mp_mul(tmp, key->q, tmp)) != CRYPT_OK) { goto error; }
if ((err = mp_add(tmp, tmpb, tmp)) != CRYPT_OK) { goto error; }
}
#ifdef LTC_RSA_BLINDING
/* unblind */