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gen_prime: check small primes early (3x speed-up)

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This commit is contained in:
Manuel Pégourié-Gonnard 2013-11-22 19:58:22 +01:00
parent 378fb4b70a
commit ddf7615d49
1 changed files with 10 additions and 7 deletions
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17
library/bignum.c
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@ -2000,20 +2000,23 @@ int mpi_gen_prime( mpi *X, size_t nbits, int dh_flag,
while( 1 )
{
if( ( ret = mpi_is_prime( X, f_rng, p_rng ) ) == 0 )
/*
* First, check small factors for X and Y
* before doing Miller-Rabin on any of them
*/
if( ( ret = mpi_check_small_factors( X ) ) == 0 &&
( ret = mpi_check_small_factors( &Y ) ) == 0 &&
( ret = mpi_miller_rabin( X, f_rng, p_rng ) ) == 0 &&
( ret = mpi_miller_rabin( &Y, f_rng, p_rng ) ) == 0 )
{
if( ( ret = mpi_is_prime( &Y, f_rng, p_rng ) ) == 0 )
break;
if( ret != POLARSSL_ERR_MPI_NOT_ACCEPTABLE )
goto cleanup;
break;
}
if( ret != POLARSSL_ERR_MPI_NOT_ACCEPTABLE )
goto cleanup;
/*
* Next candidates. We want to preserve
* Next candidates. We want to preserve Y = (X-1) / 2 and
* Y = 1 mod 2 and Y = 2 mod 3 (eq X = 3 mod 4 and X = 2 mod 3)
* so up Y by 6 and X by 12.
*/