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Added fast mod_p192

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This commit is contained in:
Manuel Pégourié-Gonnard
2012-11-11 20:45:18 +01:00
committed by Paul Bakker
parent 4712325777
commit 8433824d5f
3 changed files with 115 additions and 1 deletions
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79
library/ecp.c
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@ -36,6 +36,7 @@
#if defined(POLARSSL_ECP_C)
#include "polarssl/ecp.h"
#include <limits.h>
/*
* Initialize (the components of) a point
@ -183,10 +184,84 @@ cleanup:
return( ret );
}
/*
* 192 bits in terms of t_uint
*/
#define P192_SIZE_INT ( 192 / CHAR_BIT / sizeof( t_uint ) )
/*
* Table to get S1, S2, S3 of FIPS 186-3 D.2.1:
* -1 means let this chunk be 0
* a positive value i means A_i.
*/
#define P192_CHUNKS 3
#define P192_CHUNK_CHAR ( 64 / CHAR_BIT )
#define P192_CHUNK_INT ( P192_CHUNK_CHAR / sizeof( t_uint ) )
const signed char p192_tbl[][P192_CHUNKS] = {
{ -1, 3, 3 }, /* S1 */
{ 4, 4, -1 }, /* S2 */
{ 5, 5, 5 }, /* S3 */
};
/*
* Fast quasi-reduction modulo p192 (FIPS 186-3 D.2.1)
*/
static int ecp_mod_p192( mpi *N )
{
int ret;
unsigned char i, j, offset;
signed char chunk;
mpi tmp, acc;
t_uint tmp_p[P192_SIZE_INT], acc_p[P192_SIZE_INT + 1];
tmp.s = 1;
tmp.n = sizeof( tmp_p ) / sizeof( tmp_p[0] );
tmp.p = tmp_p;
acc.s = 1;
acc.n = sizeof( acc_p ) / sizeof( acc_p[0] );
acc.p = acc_p;
MPI_CHK( mpi_grow( N, P192_SIZE_INT * 2 ) );
/*
* acc = T
*/
memset( acc_p, 0, sizeof( acc_p ) );
memcpy( acc_p, N->p, P192_CHUNK_CHAR * P192_CHUNKS );
for( i = 0; i < sizeof( p192_tbl ) / sizeof( p192_tbl[0] ); i++)
{
/*
* tmp = S_i
*/
memset( tmp_p, 0, sizeof( tmp_p ) );
for( j = 0, offset = P192_CHUNKS - 1; j < P192_CHUNKS; j++, offset-- )
{
chunk = p192_tbl[i][j];
if( chunk >= 0 )
memcpy( tmp_p + offset * P192_CHUNK_INT,
N->p + chunk * P192_CHUNK_INT,
P192_CHUNK_CHAR );
}
/*
* acc += tmp
*/
MPI_CHK( mpi_add_abs( &acc, &acc, &tmp ) );
}
MPI_CHK( mpi_copy( N, &acc ) );
cleanup:
return( ret );
}
/*
* Size of p521 in terms of t_uint
*/
#define P521_SIZE_INT ( 521 / ( sizeof( t_uint ) << 3 ) + 1 )
#define P521_SIZE_INT ( 521 / CHAR_BIT / sizeof( t_uint ) + 1 )
/*
* Bits to keep in the most significant t_uint
@ -318,6 +393,8 @@ int ecp_use_known_dp( ecp_group *grp, size_t index )
switch( index )
{
case POLARSSL_ECP_DP_SECP192R1:
grp->modp = ecp_mod_p192;
grp->pbits = 192;
return( ecp_group_read_string( grp, 16,
SECP192R1_P, SECP192R1_B,
SECP192R1_GX, SECP192R1_GY, SECP192R1_N ) );