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fix prime number generation

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NIIBE Yutaka
2013-09-30 16:10:37 +09:00
parent f207c4ec49
commit c8a6146d02
2 changed files with 31 additions and 9 deletions
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8
ChangeLog
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@@ -1,3 +1,11 @@
2013-09-30 Niibe Yutaka <gniibe@fsij.org>
* polarssl/library/bignum.c (mpi_is_prime): Enable trial divisions
by small integers.
Add Fermat primality test.
(mpi_gen_prime): Limit random value so that two MSBs of result will
be 0x11.
2013-09-27 Niibe Yutaka <gniibe@fsij.org>
* polarssl/include/polarssl/bignum.h (mpi_is_prime): ifdef-out.

32
polarssl/library/bignum.c
View File

@@ -1805,6 +1805,7 @@ int mpi_is_prime( mpi *X,
mpi_init( &RR );
xs = X->s; X->s = 1;
ret = 0;
#if 0
/*
@@ -1812,8 +1813,10 @@ int mpi_is_prime( mpi *X,
*/
if( ( X->p[0] & 1 ) == 0 )
return( POLARSSL_ERR_MPI_NOT_ACCEPTABLE );
#endif
for( i = 0; small_prime[i] > 0; i++ )
#define SMALL_PRIME_START 124
for( i = SMALL_PRIME_START; small_prime[i] > 0; i++ )
{
t_uint r;
@@ -1825,7 +1828,6 @@ int mpi_is_prime( mpi *X,
if( r == 0 )
return( POLARSSL_ERR_MPI_NOT_ACCEPTABLE );
}
#endif
/*
* W = |X| - 1
@@ -1835,8 +1837,18 @@ int mpi_is_prime( mpi *X,
s = mpi_lsb( &W );
MPI_CHK( mpi_copy( &R, &W ) );
MPI_CHK( mpi_shift_r( &R, s ) );
i = mpi_msb( X );
/* Fermat primality test with 2. */
mpi_lset (&T, 2);
MPI_CHK( mpi_exp_mod( &T, &T, &W, X, &RR ) );
if ( mpi_cmp_int (&T, 1) != 0)
{
ret = POLARSSL_ERR_MPI_NOT_ACCEPTABLE;
goto cleanup;
}
/*
* HAC, table 4.4
*/
@@ -1969,17 +1981,19 @@ int mpi_gen_prime( mpi *X, size_t nbits, int dh_flag,
while (mpi_cmp_int ( G, 1 ) != 0);
/*
* Get random value 0 to MAX_A avoiding bias, comput P with the value,
* and check if it's prime.
* Get random value avoiding bias, comput P with the value,
* check if it's big enough, lastly, check if it's prime.
*/
while (1)
{
MPI_CHK( mpi_fill_random( X, MAX_A_SIZE, f_rng, p_rng ) );
X->p[MAX_A_LIMBS - 1] &= 0x7fffffff;
if (mpi_cmp_abs (X, MAX_A) > 0)
continue;
MPI_CHK ( mpi_mul_mpi (X, X, M) );
X->p[MAX_A_LIMBS - 1] &= 0x1fffffff;
MPI_CHK ( mpi_sub_abs (X, MAX_A, X) );
MPI_CHK ( mpi_mul_mpi ( X, X, M ) );
MPI_CHK ( mpi_add_abs ( X, X, B ) );
if (X->n <= 31 || (X->p[31] & 0xc0000000) == 0)
continue;
ret = mpi_is_prime ( X, f_rng, p_rng );
if (ret == 0 || ret != POLARSSL_ERR_MPI_NOT_ACCEPTABLE)