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RSA in case CRT optimization parameters are not populated #53

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RSA in case CRT optimization parameters are not populated #53

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7baeb0a
RSA in case CRT optimization parameters are not populated
Sep 18, 2014
caf57e2
RSA in CRT optimization parameters are empty
Sep 18, 2014
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34 changes: 21 additions & 13 deletions src/pk/rsa/rsa_exptmod.c
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Original file line number Diff line number Diff line change
Expand Up @@ -100,19 +100,27 @@ 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; }

/* 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 = 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; }
if ((key->dP == NULL) || (mp_get_digit_count(key->dP) == 0)) {
/*
* In case CRT optimization parameters are not provided,
* the private key is directly used to 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; }

/* 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; }
}

#ifdef LTC_RSA_BLINDING
/* unblind */
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