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Point multiplication using Jacobian coordinates

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Manuel Pégourié-Gonnard 2012-11-08 23:27:28 +01:00 committed by Paul Bakker
parent 7e0adfbcc5
commit e0c16922f9
2 changed files with 8 additions and 14 deletions
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6
include/polarssl/ecp.h
View file

@ -245,9 +245,6 @@ int ecp_use_known_dp( ecp_group *grp, size_t index );
*
* \return 0 if successful,
* POLARSSL_ERR_MPI_MALLOC_FAILED if memory allocation failed,
* POLARSSL_ERR_MPI_DIVISION_BY_ZERO (shouldn't happen)
* (temporary, a faster version not using division will be
* used in the future)
*/
int ecp_add( const ecp_group *grp, ecp_point *R,
const ecp_point *P, const ecp_point *Q );
@ -262,9 +259,6 @@ int ecp_add( const ecp_group *grp, ecp_point *R,
*
* \return 0 if successful,
* POLARSSL_ERR_MPI_MALLOC_FAILED if memory allocation failed,
* POLARSSL_ERR_MPI_DIVISION_BY_ZERO (shouldn't happen)
* (temporary, a faster version not using division will be
* used in the future)
*/
int ecp_mul( const ecp_group *grp, ecp_point *R,
const mpi *m, const ecp_point *P );

16
library/ecp.c
View file

@ -464,9 +464,9 @@ int ecp_mul( const ecp_group *grp, ecp_point *R,
{
int ret = 0;
size_t pos;
ecp_point Q[2];
ecp_ptjac Q[2];
ecp_point_init( &Q[0] ); ecp_point_init( &Q[1] );
ecp_ptjac_init( &Q[0] ); ecp_ptjac_init( &Q[1] );
/*
* The general method works only for m >= 1
@ -476,23 +476,23 @@ int ecp_mul( const ecp_group *grp, ecp_point *R,
goto cleanup;
}
ecp_set_zero( &Q[0] );
ecp_ptjac_set_zero( &Q[0] );
for( pos = mpi_msb( m ) - 1 ; ; pos-- )
{
MPI_CHK( ecp_add( grp, &Q[0], &Q[0], &Q[0] ) );
MPI_CHK( ecp_add( grp, &Q[1], &Q[0], P ) );
MPI_CHK( ecp_copy( &Q[0], &Q[ mpi_get_bit( m, pos ) ] ) );
MPI_CHK( ecp_double_jac( grp, &Q[0], &Q[0] ) );
MPI_CHK( ecp_add_mixed( grp, &Q[1], &Q[0], P ) );
MPI_CHK( ecp_ptjac_copy( &Q[0], &Q[ mpi_get_bit( m, pos ) ] ) );
if( pos == 0 )
break;
}
MPI_CHK( ecp_copy( R, &Q[0] ) );
MPI_CHK( ecp_jac_to_aff( grp, R, &Q[0] ) );
cleanup:
ecp_point_free( &Q[0] ); ecp_point_free( &Q[1] );
ecp_ptjac_free( &Q[0] ); ecp_ptjac_free( &Q[1] );
return( ret );
}