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Reduce the size of the small primes table used by primality testing

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Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2019-02-08 17:27:11 +01:00
parent 7ef14bf8a2
commit b2bc1712a5
1 changed files with 31 additions and 31 deletions
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60
library/bignum.c
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@ -2171,29 +2171,29 @@ cleanup:
#if defined(MBEDTLS_GENPRIME) #if defined(MBEDTLS_GENPRIME)
static const int small_prime[] = /* Gaps between primes, starting at 3. https://oeis.org/A001223 */
{ static const unsigned char small_prime_gaps[] = {
3, 5, 7, 11, 13, 17, 19, 23, 2, 2, 4, 2, 4, 2, 4, 6,
29, 31, 37, 41, 43, 47, 53, 59, 2, 6, 4, 2, 4, 6, 6, 2,
61, 67, 71, 73, 79, 83, 89, 97, 6, 4, 2, 6, 4, 6, 8, 4,
101, 103, 107, 109, 113, 127, 131, 137, 2, 4, 2, 4, 14, 4, 6, 2,
139, 149, 151, 157, 163, 167, 173, 179, 10, 2, 6, 6, 4, 6, 6, 2,
181, 191, 193, 197, 199, 211, 223, 227, 10, 2, 4, 2, 12, 12, 4, 2,
229, 233, 239, 241, 251, 257, 263, 269, 4, 6, 2, 10, 6, 6, 6, 2,
271, 277, 281, 283, 293, 307, 311, 313, 6, 4, 2, 10, 14, 4, 2, 4,
317, 331, 337, 347, 349, 353, 359, 367, 14, 6, 10, 2, 4, 6, 8, 6,
373, 379, 383, 389, 397, 401, 409, 419, 6, 4, 6, 8, 4, 8, 10, 2,
421, 431, 433, 439, 443, 449, 457, 461, 10, 2, 6, 4, 6, 8, 4, 2,
463, 467, 479, 487, 491, 499, 503, 509, 4, 12, 8, 4, 8, 4, 6, 12,
521, 523, 541, 547, 557, 563, 569, 571, 2, 18, 6, 10, 6, 6, 2, 6,
577, 587, 593, 599, 601, 607, 613, 617, 10, 6, 6, 2, 6, 6, 4, 2,
619, 631, 641, 643, 647, 653, 659, 661, 12, 10, 2, 4, 6, 6, 2, 12,
673, 677, 683, 691, 701, 709, 719, 727, 4, 6, 8, 10, 8, 10, 8, 6,
733, 739, 743, 751, 757, 761, 769, 773, 6, 4, 8, 6, 4, 8, 4, 14,
787, 797, 809, 811, 821, 823, 827, 829, 10, 12, 2, 10, 2, 4, 2, 10,
839, 853, 857, 859, 863, 877, 881, 883, 14, 4, 2, 4, 14, 4, 2, 4,
887, 907, 911, 919, 929, 937, 941, 947, 20, 4, 8, 10, 8, 4, 6, 6,
953, 967, 971, 977, 983, 991, 997, -103 14, 4, 6, 6, 8, 6, /*reaches 997*/
}; };
/* /*
@ -2210,22 +2210,22 @@ static int mpi_check_small_factors(const mbedtls_mpi *X)
int ret = 0; int ret = 0;
size_t i; size_t i;
mbedtls_mpi_uint r; mbedtls_mpi_uint r;
unsigned p = 3; /* The first odd prime */
if ((X->p[0] & 1) == 0) { if ((X->p[0] & 1) == 0) {
return MBEDTLS_ERR_MPI_NOT_ACCEPTABLE; return MBEDTLS_ERR_MPI_NOT_ACCEPTABLE;
} }
for (i = 0; small_prime[i] > 0; i++) { for (i = 0; i < sizeof(small_prime_gaps); p += small_prime_gaps[i], i++) {
if (mbedtls_mpi_cmp_int(X, small_prime[i]) <= 0) { MBEDTLS_MPI_CHK(mbedtls_mpi_mod_int(&r, X, p));
return 1;
}
MBEDTLS_MPI_CHK(mbedtls_mpi_mod_int(&r, X, small_prime[i]));
if (r == 0) { if (r == 0) {
if (mbedtls_mpi_cmp_int(X, p) == 0) {
return 1;
} else {
return MBEDTLS_ERR_MPI_NOT_ACCEPTABLE; return MBEDTLS_ERR_MPI_NOT_ACCEPTABLE;
} }
} }
}
cleanup: cleanup:
return ret; return ret;