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Fixed add_generic

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Manuel Pégourié-Gonnard 2012-11-05 17:34:55 +01:00 committed by Paul Bakker
parent b505c2796c
commit ab38b70816
1 changed files with 24 additions and 16 deletions
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40
library/ecp.c
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@ -154,6 +154,8 @@ cleanup:
return( ret );
}
#define dbg(X) printf(#X " = %s%lu\n", X.s < 0 ? "-" : "", X.p[0])
/*
* Addition: R = P + Q, generic case (P != Q, P != 0, Q != 0, R != 0)
* Cf SEC1 v2 p. 7, item 4
@ -162,10 +164,10 @@ static int ecp_add_generic( const ecp_group *grp, ecp_point *R,
const ecp_point *P, const ecp_point *Q )
{
int ret = 0;
mpi DX, DY, K, L, LL, M, X, Y;
mpi DX, DY, K, L, LL, X, Y;
mpi_init( &DX ); mpi_init( &DY ); mpi_init( &K ); mpi_init( &L );
mpi_init( &LL ); mpi_init( &M ); mpi_init( &X ); mpi_init( &Y );
mpi_init( &LL ); mpi_init( &X ); mpi_init( &Y );
/*
* L = (Q.Y - P.Y) / (Q.X - P.X) mod p
@ -178,19 +180,21 @@ static int ecp_add_generic( const ecp_group *grp, ecp_point *R,
/*
* LL = L^2 mod p
* M = L^2 - Q.X
* X = L^2 - P.X - Q.X
*/
MPI_CHK( mpi_mul_mpi( &LL, &L, &L ) );
MPI_CHK( mpi_mod_mpi( &LL, &LL, &grp->P ) );
MPI_CHK( mpi_sub_mpi( &M, &LL, &Q->X ) );
MPI_CHK( mpi_sub_mpi( &X, &M, &P->X ) );
/*
* Y = L * (P.X - X) - P.Y = L * (-M) - P.Y
* X = L^2 - P.X - Q.X
*/
MPI_CHK( mpi_copy( &Y, &M ) );
Y.s = - Y.s;
MPI_CHK( mpi_sub_mpi( &X, &LL, &P->X ) );
MPI_CHK( mpi_sub_mpi( &X, &X, &Q->X ) );
/*
* Y = L * (P.X - X) - P.Y
*/
MPI_CHK( mpi_sub_mpi( &Y, &P->X, &X) );
MPI_CHK( mpi_mul_mpi( &Y, &Y, &L ) );
MPI_CHK( mpi_sub_mpi( &Y, &Y, &P->Y ) );
@ -204,7 +208,7 @@ static int ecp_add_generic( const ecp_group *grp, ecp_point *R,
cleanup:
mpi_free( &DX ); mpi_free( &DY ); mpi_free( &K ); mpi_free( &L );
mpi_free( &LL ); mpi_free( &M ); mpi_free( &X ); mpi_free( &Y );
mpi_free( &LL ); mpi_free( &X ); mpi_free( &Y );
return( ret );
}
@ -276,14 +280,14 @@ static int ecp_point_eq( const ecp_point *P, const ecp_point *Q )
}
/*
* Print a point assuming its components are small
* Print a point assuming its coordinates are small
*/
static void ecp_point_print( const ecp_point *P )
{
if( P->is_zero )
printf("zero\n");
printf( "zero\n" );
else
printf("(%lu, %lu)\n", P->X.p[0], P->Y.p[0]);
printf( "(%lu, %lu)\n", P->X.p[0], P->Y.p[0] );
}
@ -302,7 +306,11 @@ int ecp_self_test( int verbose )
ecp_point O, A, B, C, D, E, F, G, TMP;
ecp_point *add_tbl[][3] =
{
{&O, &O, &O},
{&O, &O, &O}, {&O, &A, &A}, {&A, &O, &A},
{&A, &A, &O}, {&B, &C, &O}, {&C, &B, &O},
{&A, &D, &E}, {&D, &A, &E},
{&B, &D, &F}, {&D, &B, &F},
// {&D, &D, &G},
};
ecp_group_init( &grp );
@ -330,10 +338,10 @@ int ecp_self_test( int verbose )
{
if( verbose != 0 )
{
printf(" failed\n");
printf(" GOT: ");
printf(" failed (%u)\n", i );
printf( " GOT: " );
ecp_point_print( &TMP );
printf(" EXPECTED: ");
printf( " EXPECTED: " );
ecp_point_print( add_tbl[i][2] );
}