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RSA: check for small difference between p and q

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This commit is contained in:
Sean Parkinson
2022-03-15 10:06:32 +10:00
parent 34e491f39f
commit 8dbd8b0ad6
1 changed files with 45 additions and 9 deletions
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54
wolfcrypt/src/rsa.c
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@ -59,15 +59,20 @@ RSA keys can be used to encrypt, decrypt, sign and verify data.
/*
Possible RSA enable options:
* NO_RSA: Overall control of RSA default: on (not defined)
* WC_RSA_BLINDING: Uses Blinding w/ Private Ops default: off
Note: slower by ~20%
* WOLFSSL_KEY_GEN: Allows Private Key Generation default: off
* RSA_LOW_MEM: NON CRT Private Operations, less memory default: off
* WC_NO_RSA_OAEP: Disables RSA OAEP padding default: on (not defined)
* WC_RSA_NONBLOCK: Enables support for RSA non-blocking default: off
* WC_RSA_NONBLOCK_TIME:Enables support for time based blocking default: off
* time calculation.
* NO_RSA: Overall control of RSA default: on
* (not defined)
* WC_RSA_BLINDING: Uses Blinding w/ Private Ops default: off
Note: slower by ~20%
* WOLFSSL_KEY_GEN: Allows Private Key Generation default: off
* RSA_LOW_MEM: NON CRT Private Operations, less memory default: off
* WC_NO_RSA_OAEP: Disables RSA OAEP padding default: on
* (not defined)
* WC_RSA_NONBLOCK: Enables support for RSA non-blocking default: off
* WC_RSA_NONBLOCK_TIME: Enables support for time based blocking default: off
* time calculation.
* WC_RSA_NO_FERMAT_CHECK:Don't check for small difference in default: off
* p and q (Fermat's factorization is (not defined)
* possible when small difference).
*/
/*
@ -731,6 +736,22 @@ int wc_CheckRsaKey(RsaKey* key)
}
}
#ifdef WC_RSA_NO_FERMAT_CHECK
/* Fermat's Factorization works when difference between p and q
* is less than (conservatively):
* n^(1/4) + 32
* ~= 2^(bit count of n)^(1/4) + 32) = 2^((bit count of n)/4 + 32)
*/
if (ret == 0) {
ret = mp_sub(&key->p, &key->q, tmp);
}
if (ret == 0) {
if (mp_count_bits(tmp) <= (mp_count_bits(&key->n) / 4 + 32)) {
ret = MP_EXPTMOD_E;
}
}
#endif
/* Check dP, dQ and u if they exist */
if (ret == 0 && !mp_iszero(&key->dP)) {
if (mp_sub_d(&key->p, 1, tmp) != MP_OKAY) {
@ -4526,6 +4547,21 @@ int wc_MakeRsaKey(RsaKey* key, int size, long e, WC_RNG* rng)
if (err == MP_OKAY)
err = _CheckProbablePrime(p, q, tmp3, size, &isPrime, rng);
#ifdef WC_RSA_NO_FERMAT_CHECK
if (err == MP_OKAY && isPrime) {
/* Fermat's Factorization works when difference between p and q
* is less than (conservatively):
* n^(1/4) + 32
* ~= 2^(bit count of n)^(1/4) + 32)
* = 2^((bit count of n)/4 + 32)
*/
err = mp_sub(p, q, tmp1);
if (err == MP_OKAY && mp_count_bits(tmp1) <= (size / 4) + 32) {
isPrime = 0;
}
}
#endif
#ifdef HAVE_FIPS
i++;
#else