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Full restart support in ecp_mul_comb_core()

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Still recomputing table every time, though.
This commit is contained in:
Manuel Pégourié-Gonnard 2017-03-15 13:06:28 +01:00
parent 2fad7ae02a
commit c5d844b999
1 changed files with 35 additions and 9 deletions
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44
library/ecp.c
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@ -108,6 +108,7 @@ struct mbedtls_ecp_restart {
mbedtls_mpi m; /* saved argument: scalar */
mbedtls_ecp_point P; /* saved argument: point */
mbedtls_ecp_point R; /* current intermediate result */
size_t i; /* current index in various loops, 0 outside */
enum {
ecp_rs_init = 0,
ecp_rs_final_norm,
@ -1409,15 +1410,26 @@ static int ecp_mul_comb_core( const mbedtls_ecp_group *grp, mbedtls_ecp_point *R
mbedtls_ecp_point_init( &Txi );
/* Start with a non-zero point and randomize its coordinates */
i = d;
MBEDTLS_MPI_CHK( ecp_select_comb( grp, R, T, t_len, x[i] ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &R->Z, 1 ) );
if( f_rng != 0 )
MBEDTLS_MPI_CHK( ecp_randomize_jac( grp, R, f_rng, p_rng ) );
#if defined(MBEDTLS_ECP_EARLY_RETURN)
if( grp->rs != NULL && grp->rs->i != 0 )
{
/* restore current index (R already pointing to grp->rs->R) */
i = grp->rs->i;
}
else
#endif
{
/* Start with a non-zero point and randomize its coordinates */
i = d;
MBEDTLS_MPI_CHK( ecp_select_comb( grp, R, T, t_len, x[i] ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_lset( &R->Z, 1 ) );
if( f_rng != 0 )
MBEDTLS_MPI_CHK( ecp_randomize_jac( grp, R, f_rng, p_rng ) );
}
while( i-- != 0 )
{
ECP_BUDGET( ECP_OPS_DBL + ECP_OPS_ADD );
MBEDTLS_MPI_CHK( ecp_double_jac( grp, R, R ) );
MBEDTLS_MPI_CHK( ecp_select_comb( grp, &Txi, T, t_len, x[i] ) );
MBEDTLS_MPI_CHK( ecp_add_mixed( grp, R, R, &Txi ) );
@ -1427,6 +1439,23 @@ cleanup:
mbedtls_ecp_point_free( &Txi );
#if defined(MBEDTLS_ECP_EARLY_RETURN)
if( grp->rs != NULL )
{
if( ret == 0 )
{
grp->rs->state++;
grp->rs->i = 0;
}
else if( ret == MBEDTLS_ERR_ECP_IN_PROGRESS )
{
/* was decreased before actually doing it */
grp->rs->i = i + 1;
/* no need to save R, already pointing to grp->rs->R */
}
}
#endif
return( ret );
}
@ -1513,9 +1542,6 @@ static int ecp_mul_comb_after_precomp( const mbedtls_ecp_group *grp,
if( grp->rs != NULL )
grp->rs->state++;
#endif
/* XXX: temporary: should have counted some ops */
ECP_BUDGET( 42 );
}
ECP_BUDGET( ECP_OPS_INV );