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static initialize comb table

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MBEDTLS_ECP_FIXED_POINT_OPTIM aims to speed up ecc multiplication performance.

We compute the comb table in runtime now. It is a costly operation.

This patch add a pre-computed table to initialize well-known curves. It speed up ECDSA signature verify process in runtime by using more ROM size.

Signed-off-by: kXuan <kxuanobj@gmail.com>
This commit is contained in:
kXuan 2021-04-08 14:32:06 +08:00
parent 6d84e917bb
commit ba9cb76e9f
No known key found for this signature in database
GPG Key ID: E53EA872AFCA251C
4 changed files with 4035 additions and 27 deletions
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8
include/mbedtls/ecp.h
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@ -229,7 +229,7 @@ typedef struct mbedtls_ecp_group
int (*t_post)(mbedtls_ecp_point *, void *); /*!< Unused. */
void *t_data; /*!< Unused. */
mbedtls_ecp_point *T; /*!< Pre-computed points for ecp_mul_comb(). */
size_t T_size; /*!< The number of pre-computed points. */
size_t T_size; /*!< The number of dynamic allocated pre-computed points. */
}
mbedtls_ecp_group;
@ -276,15 +276,15 @@ mbedtls_ecp_group;
#if !defined(MBEDTLS_ECP_FIXED_POINT_OPTIM)
/*
* Trade memory for speed on fixed-point multiplication.
* Trade ROM usage for speed on fixed-point multiplication.
*
* This speeds up repeated multiplication of the generator (that is, the
* multiplication in ECDSA signatures, and half of the multiplications in
* ECDSA verification and ECDHE) by a factor roughly 3 to 4.
*
* The cost is increasing EC peak memory usage by a factor roughly 2.
* The cost is increasing ROM usage by a factor roughly 2.
*
* Change this value to 0 to reduce peak memory usage.
* Change this value to 0 to reduce ROM usage.
*/
#define MBEDTLS_ECP_FIXED_POINT_OPTIM 1 /**< Enable fixed-point speed-up. */
#endif /* MBEDTLS_ECP_FIXED_POINT_OPTIM */

23
library/ecp.c
View File

@ -728,6 +728,18 @@ void mbedtls_ecp_point_free( mbedtls_ecp_point *pt )
mbedtls_mpi_free( &( pt->Z ) );
}
/*
* Check that the comb table (grp->T) is static initialized.
*/
static int ecp_group_is_static_comb_table( const mbedtls_ecp_group *grp ) {
#if MBEDTLS_ECP_FIXED_POINT_OPTIM == 1
return grp->T != NULL && grp->T_size == 0;
#else
(void) grp;
return 0;
#endif
}
/*
* Unallocate (the components of) a group
*/
@ -747,7 +759,7 @@ void mbedtls_ecp_group_free( mbedtls_ecp_group *grp )
mbedtls_mpi_free( &grp->N );
}
if( grp->T != NULL )
if( !ecp_group_is_static_comb_table(grp) && grp->T != NULL )
{
for( i = 0; i < grp->T_size; i++ )
mbedtls_ecp_point_free( &grp->T[i] );
@ -2245,11 +2257,16 @@ static unsigned char ecp_pick_window_size( const mbedtls_ecp_group *grp,
w++;
/*
* Make sure w is within bounds.
* If static comb table may not be used (!p_eq_g) or static comb table does
* not exists, make sure w is within bounds.
* (The last test is useful only for very small curves in the test suite.)
*
* The user reduces MBEDTLS_ECP_WINDOW_SIZE does not changes the size of
* static comb table, because the size of static comb table is fixed when
* it is generated.
*/
#if( MBEDTLS_ECP_WINDOW_SIZE < 6 )
if( w > MBEDTLS_ECP_WINDOW_SIZE )
if( (!p_eq_g || !ecp_group_is_static_comb_table(grp)) && w > MBEDTLS_ECP_WINDOW_SIZE )
w = MBEDTLS_ECP_WINDOW_SIZE;
#endif
if( w >= grp->nbits )

4025
library/ecp_curves.c
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File diff suppressed because it is too large Load Diff

6
programs/test/benchmark.c
View File

@ -251,7 +251,11 @@ static int myrand( void *rng_state, unsigned char *output, size_t len )
#if defined(MBEDTLS_ECP_C)
void ecp_clear_precomputed( mbedtls_ecp_group *grp )
{
if( grp->T != NULL )
if( grp->T != NULL
#if MBEDTLS_ECP_FIXED_POINT_OPTIM == 1
&& grp->T_size != 0
#endif
)
{
size_t i;
for( i = 0; i < grp->T_size; i++ )