AuroraMiddleware/mbedtls
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Move more code to separate function

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This reduces the scope of some variables (M, k), clarifying where they're
used.
This commit is contained in:
Manuel Pégourié-Gonnard 2017-03-13 12:26:21 +01:00
parent 24be79588d
commit 391f44153d
1 changed files with 53 additions and 26 deletions
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79
library/ecp.c
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@ -1407,6 +1407,53 @@ cleanup:
return( ret );
}
/*
* Perform comb multiplication (for short Weierstrass curves)
* once the auxiliary table has been pre-computed.
*/
static int ecp_mul_comb_after_precomp( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *R,
const mbedtls_mpi *m,
const mbedtls_ecp_point *T,
unsigned char pre_len,
unsigned char w,
size_t d,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret;
unsigned char m_is_odd;
unsigned char k[COMB_MAX_D + 1];
mbedtls_mpi M;
mbedtls_mpi_init( &M );
/*
* We need an odd scalar for recoding. Ensure that by replacing it with
* its opposite, then negating the result to compensate if needed.
*/
m_is_odd = ( mbedtls_mpi_get_bit( m, 0 ) == 1 );
MBEDTLS_MPI_CHK( ecp_make_scalar_odd( grp, &M, m, m_is_odd ) );
ecp_comb_fixed( k, d, w, &M );
/*
* Go for comb multiplication, R = M * P
*/
MBEDTLS_MPI_CHK( ecp_mul_comb_core( grp, R, T, pre_len, k, d, f_rng, p_rng ) );
/*
* Now get m * P from M * P and normalize it
*/
MBEDTLS_MPI_CHK( ecp_safe_invert_jac( grp, R, ! m_is_odd ) );
MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, R ) );
cleanup:
mbedtls_mpi_free( &M );
return( ret );
}
/*
* Pick window size based on curve size and whether we optimize for base point
*/
@ -1452,19 +1499,15 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
void *p_rng )
{
int ret;
unsigned char w, m_is_odd, p_eq_g, pre_len, i;
unsigned char w, p_eq_g, pre_len, i;
size_t d;
unsigned char k[COMB_MAX_D + 1];
mbedtls_ecp_point *T = NULL;
mbedtls_mpi M;
#if defined(MBEDTLS_ECP_EARLY_RETURN)
if( ecp_restart.fake_it++ != 0 && ecp_max_ops != 0 )
return( MBEDTLS_ERR_ECP_IN_PROGRESS );
#endif
mbedtls_mpi_init( &M );
/* Is P the base point ? */
#if MBEDTLS_ECP_FIXED_POINT_OPTIM == 1
p_eq_g = ( mbedtls_mpi_cmp_mpi( &P->Y, &grp->G.Y ) == 0 &&
@ -1473,7 +1516,7 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
p_eq_g = 0;
#endif
/* Window size and others that depend on it */
/* Pick window size and deduce related sizes */
w = ecp_pick_window_size( grp, p_eq_g );
pre_len = 1U << ( w - 1 );
d = ( grp->nbits + w - 1 ) / w;
@ -1502,24 +1545,10 @@ static int ecp_mul_comb( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
}
}
/*
* We need an odd scalar for recoding. Ensure that by replacing it with
* its opposite, then negating the result to compensate if needed.
*/
m_is_odd = ( mbedtls_mpi_get_bit( m, 0 ) == 1 );
MBEDTLS_MPI_CHK( ecp_make_scalar_odd( grp, &M, m, m_is_odd ) );
/*
* Go for comb multiplication, R = M * P
*/
ecp_comb_fixed( k, d, w, &M );
MBEDTLS_MPI_CHK( ecp_mul_comb_core( grp, R, T, pre_len, k, d, f_rng, p_rng ) );
/*
* Now get m * P from M * P and normalize it
*/
MBEDTLS_MPI_CHK( ecp_safe_invert_jac( grp, R, ! m_is_odd ) );
MBEDTLS_MPI_CHK( ecp_normalize_jac( grp, R ) );
/* Actual comb multiplication using precomputed points */
MBEDTLS_MPI_CHK( ecp_mul_comb_after_precomp( grp, R, m,
T, pre_len, w, d,
f_rng, p_rng ) );
cleanup:
@ -1530,8 +1559,6 @@ cleanup:
mbedtls_free( T );
}
mbedtls_mpi_free( &M );
if( ret != 0 )
mbedtls_ecp_point_free( R );