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mbedtls: add naive double and add method for ec to safe RAM - used when MBEDTLS_ECP_WINDOW_SIZE == 1

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This commit is contained in:
Matthias Ringwald 2016-06-29 10:55:40 +02:00
parent aa7d4d9c48
commit 1bf28f67a5
2 changed files with 87 additions and 15 deletions
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3
3rd-party/mbedtls/include/mbedtls/config.h vendored
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@ -2456,7 +2456,8 @@ void sm_mbedtls_allocator_free(void * data);
/* ECP options */
//#define MBEDTLS_ECP_MAX_BITS 521 /**< Maximum bit size of groups */
#define MBEDTLS_ECP_WINDOW_SIZE 2 /**< Maximum window size used */
#define MBEDTLS_ECP_WINDOW_SIZE 1 /**< Maximum window size used - 1 == uses double and add to save RAM */
#define MBEDTLS_ECP_MUL_NAIVE_SAFE 0 /**< Enable use of temporary point for window size == 1 - adds ~100 bytes but makes branches independ from n */
#define MBEDTLS_ECP_FIXED_POINT_OPTIM 0 /**< Enable fixed-point speed-up */
/* Entropy options */

99
3rd-party/mbedtls/library/ecp.c vendored
View File

@ -728,6 +728,25 @@ cleanup:
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_abs( &N, &N, &grp->P ) )
#if defined(ECP_SHORTWEIERSTRASS)
/*
* Check and define parameters used by the comb method (see below for details)
*/
#if MBEDTLS_ECP_WINDOW_SIZE > 7
#error "MBEDTLS_ECP_WINDOW_SIZE out of bounds"
#endif
#if MBEDTLS_ECP_WINDOW_SIZE >= 2
#define ECP_COMB_METHOD
/* d = ceil( n / w ) */
#define COMB_MAX_D ( MBEDTLS_ECP_MAX_BITS + 1 ) / 2
/* number of precomputed points */
#define COMB_MAX_PRE ( 1 << ( MBEDTLS_ECP_WINDOW_SIZE - 1 ) )
#endif
/*
* For curves in short Weierstrass form, we do all the internal operations in
* Jacobian coordinates.
@ -775,6 +794,7 @@ cleanup:
return( ret );
}
#ifdef ECP_COMB_METHOD
/*
* Normalize jacobian coordinates of an array of (pointers to) points,
* using Montgomery's trick to perform only one inversion mod P.
@ -887,6 +907,7 @@ cleanup:
return( ret );
}
#endif
/*
* Point doubling R = 2 P, Jacobian coordinates
@ -1068,6 +1089,8 @@ cleanup:
return( ret );
}
#ifdef ECP_COMB_METHOD
/*
* Randomize jacobian coordinates:
* (X, Y, Z) -> (l^2 X, l^3 Y, l Z) for random l
@ -1115,19 +1138,6 @@ cleanup:
return( ret );
}
/*
* Check and define parameters used by the comb method (see below for details)
*/
#if MBEDTLS_ECP_WINDOW_SIZE < 2 || MBEDTLS_ECP_WINDOW_SIZE > 7
#error "MBEDTLS_ECP_WINDOW_SIZE out of bounds"
#endif
/* d = ceil( n / w ) */
#define COMB_MAX_D ( MBEDTLS_ECP_MAX_BITS + 1 ) / 2
/* number of precomputed points */
#define COMB_MAX_PRE ( 1 << ( MBEDTLS_ECP_WINDOW_SIZE - 1 ) )
/*
* Compute the representation of m that will be used with our comb method.
*
@ -1422,6 +1432,63 @@ cleanup:
return( ret );
}
#else /* ECP_COMB_METHOD */
/*
* Multiplication using the double and add method,
* for curves in short Weierstrass form to optimize for RAM usage vs. speed
*
* Implemented by BlueKitchen GmbH
* Note:
*/
static int ecp_mul_naive( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
const mbedtls_mpi *m, const mbedtls_ecp_point *P,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret;
int i;
#if MBEDTLS_ECP_MUL_NAIVE_SAFE == 1
mbedtls_ecp_point T;
mbedtls_ecp_point_init(&T);
#endif
// calculate m * p using double and add in decreasing fashion to use ecp_add_mixed
mbedtls_ecp_point_init(R);
for (i=grp->nbits;i >= 0;i--){
MBEDTLS_MPI_CHK( ecp_double_jac( grp, R, R ) );
#if MBEDTLS_ECP_MUL_NAIVE_SAFE == 1
MBEDTLS_MPI_CHK( ecp_add_mixed(grp, &T, R, P) );
int bit_set = mbedtls_mpi_get_bit(m, i);
MBEDTLS_MPI_CHK( mbedtls_mpi_safe_cond_assign(&R->X, &T.X, bit_set));
MBEDTLS_MPI_CHK( mbedtls_mpi_safe_cond_assign(&R->Y, &T.Y, bit_set));
MBEDTLS_MPI_CHK( mbedtls_mpi_safe_cond_assign(&R->Y, &T.Y, bit_set));
#else
if (mbedtls_mpi_get_bit(m, i)){
MBEDTLS_MPI_CHK( ecp_add_mixed(grp, R, R, P) );
}
#endif
}
// normalize jacobian coordinates
MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, R ) );
cleanup:
#if MBEDTLS_ECP_MUL_NAIVE_SAFE == 1
mbedtls_ecp_point_free(&T);
#endif
if( ret != 0 )
mbedtls_ecp_point_free( R );
return( ret );
}
#endif /* ECP_COMB_METHOD */
#endif /* ECP_SHORTWEIERSTRASS */
#if defined(ECP_MONTGOMERY)
@ -1612,8 +1679,8 @@ int mbedtls_ecp_mul( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
const mbedtls_mpi *m, const mbedtls_ecp_point *P,
int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
{
int ret;
int ret;
/* Common sanity checks */
if( mbedtls_mpi_cmp_int( &P->Z, 1 ) != 0 )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
@ -1628,7 +1695,11 @@ int mbedtls_ecp_mul( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
#endif
#if defined(ECP_SHORTWEIERSTRASS)
if( ecp_get_type( grp ) == ECP_TYPE_SHORT_WEIERSTRASS )
#ifdef ECP_COMB_METHOD
return( ecp_mul_comb( grp, R, m, P, f_rng, p_rng ) );
#else
return( ecp_mul_naive( grp, R, m, P, f_rng, p_rng ) );
#endif
#endif
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
}