| /* |
| * Elliptic curves over GF(p) |
| * |
| * Copyright (C) 2012, Brainspark B.V. |
| * |
| * This file is part of PolarSSL (http://www.polarssl.org) |
| * Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org> |
| * |
| * All rights reserved. |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License along |
| * with this program; if not, write to the Free Software Foundation, Inc., |
| * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. |
| */ |
| |
| /* |
| * References: |
| * |
| * SEC1 http://www.secg.org/index.php?action=secg,docs_secg |
| * Guide to Elliptic Curve Cryptography - Hankerson, Menezes, Vanstone |
| */ |
| |
| #include "polarssl/config.h" |
| |
| #if defined(POLARSSL_ECP_C) |
| |
| #include "polarssl/ecp.h" |
| |
| /* |
| * Initialize a point |
| */ |
| void ecp_point_init( ecp_point *pt ) |
| { |
| if( pt == NULL ) |
| return; |
| |
| pt->is_zero = 1; |
| mpi_init( &( pt->X ) ); |
| mpi_init( &( pt->Y ) ); |
| } |
| |
| /* |
| * Unallocate (the components of) a point |
| */ |
| void ecp_point_free( ecp_point *pt ) |
| { |
| if( pt == NULL ) |
| return; |
| |
| pt->is_zero = 1; |
| mpi_free( &( pt->X ) ); |
| mpi_free( &( pt->Y ) ); |
| } |
| |
| /* |
| * Unallocate (the components of) a group |
| */ |
| void ecp_group_free( ecp_group *grp ) |
| { |
| if( grp == NULL ) |
| return; |
| |
| mpi_free( &grp->P ); |
| mpi_free( &grp->B ); |
| ecp_point_free( &grp->G ); |
| mpi_free( &grp->N ); |
| } |
| |
| /* |
| * Set point to zero |
| */ |
| void ecp_set_zero( ecp_point *pt ) |
| { |
| pt->is_zero = 1; |
| mpi_free( &( pt->X ) ); |
| mpi_free( &( pt->Y ) ); |
| } |
| |
| /* |
| * Copy the contents of Q into P |
| */ |
| int ecp_copy( ecp_point *P, const ecp_point *Q ) |
| { |
| int ret = 0; |
| |
| P->is_zero = Q->is_zero; |
| MPI_CHK( mpi_copy( &P->X, &Q->X ) ); |
| MPI_CHK( mpi_copy( &P->Y, &Q->Y ) ); |
| |
| cleanup: |
| return( ret ); |
| } |
| |
| /* |
| * Import a non-zero point from ASCII strings |
| */ |
| int ecp_point_read_string( ecp_point *P, int radix, |
| const char *x, const char *y ) |
| { |
| int ret = 0; |
| |
| P->is_zero = 0; |
| MPI_CHK( mpi_read_string( &P->X, radix, x ) ); |
| MPI_CHK( mpi_read_string( &P->Y, radix, y ) ); |
| |
| cleanup: |
| return( ret ); |
| } |
| |
| /* |
| * Import an ECP group from ASCII strings |
| */ |
| int ecp_group_read_string( ecp_group *grp, int radix, |
| const char *p, const char *b, |
| const char *gx, const char *gy, const char *n) |
| { |
| int ret = 0; |
| |
| MPI_CHK( mpi_read_string( &grp->P, radix, p ) ); |
| MPI_CHK( mpi_read_string( &grp->B, radix, b ) ); |
| MPI_CHK( ecp_point_read_string( &grp->G, radix, gx, gy ) ); |
| MPI_CHK( mpi_read_string( &grp->N, radix, n ) ); |
| |
| cleanup: |
| return( ret ); |
| } |
| |
| /* |
| * Addition: R = P + Q, generic case (P != Q, P != 0, Q != 0, R != 0) |
| * Cf SEC1 v2 p. 7, item 4 |
| */ |
| 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_init( &DX ); mpi_init( &DY ); mpi_init( &K ); mpi_init( &L ); |
| mpi_init( &LL ); mpi_init( &M ); mpi_init( &X ); mpi_init( &Y ); |
| |
| /* |
| * L = (Q.Y - P.Y) / (Q.X - P.X) mod p |
| */ |
| MPI_CHK( mpi_sub_mpi( &DY, &Q->Y, &P->Y ) ); |
| MPI_CHK( mpi_sub_mpi( &DX, &Q->X, &P->X ) ); |
| MPI_CHK( mpi_inv_mod( &K, &DX, &grp->P ) ); |
| MPI_CHK( mpi_mul_mpi( &K, &K, &DY ) ); |
| MPI_CHK( mpi_mod_mpi( &L, &K, &grp->P ) ); |
| |
| /* |
| * 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 |
| */ |
| MPI_CHK( mpi_copy( &Y, &M ) ); |
| Y.s = - Y.s; |
| MPI_CHK( mpi_mul_mpi( &Y, &Y, &L ) ); |
| MPI_CHK( mpi_sub_mpi( &Y, &Y, &P->Y ) ); |
| |
| /* |
| * R = (X mod p, Y mod p) |
| */ |
| R->is_zero = 0; |
| MPI_CHK( mpi_mod_mpi( &R->X, &X, &grp->P ) ); |
| MPI_CHK( mpi_mod_mpi( &R->Y, &Y, &grp->P ) ); |
| |
| 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 ); |
| |
| return( ret ); |
| } |
| |
| /* |
| * Doubling: R = 2 * P, generic case (P != 0, R != 0) |
| */ |
| static int ecp_double_generic( const ecp_group *grp, ecp_point *R, |
| const ecp_point *P ) |
| { |
| int ret = 0; |
| |
| (void) grp; |
| (void) R; |
| (void) P; |
| |
| return( ret ); |
| } |
| |
| /* |
| * Addition: R = P + Q, cf p. 7 of SEC1 v2 |
| */ |
| int ecp_add( const ecp_group *grp, ecp_point *R, |
| const ecp_point *P, const ecp_point *Q ) |
| { |
| int ret = 0; |
| |
| if( P->is_zero ) |
| { |
| ret = ecp_copy( R, Q ); |
| } |
| else if( Q->is_zero ) |
| { |
| ret = ecp_copy( R, P ); |
| } |
| else if( mpi_cmp_mpi( &P->X, &Q->X ) != 0 ) |
| { |
| ret = ecp_add_generic( grp, R, P, Q ); |
| } |
| else if( mpi_cmp_int( &P->Y, 0 ) == 0 || |
| mpi_cmp_mpi( &P->Y, &Q->Y ) != 0 ) |
| { |
| ecp_set_zero( R ); |
| } |
| else |
| { |
| /* |
| * P == Q |
| */ |
| ret = ecp_double_generic( grp, R, P ); |
| } |
| |
| return ret; |
| } |
| |
| |
| #if defined(POLARSSL_SELF_TEST) |
| |
| /* |
| * Return true iff P and Q are the same point |
| */ |
| static int ecp_point_eq( const ecp_point *P, const ecp_point *Q ) |
| { |
| if( P->is_zero || Q->is_zero ) |
| return( P->is_zero && Q->is_zero ); |
| |
| return( mpi_cmp_mpi( &P->X, &Q->X ) == 0 && |
| mpi_cmp_mpi( &P->Y, &Q->Y ) == 0 ); |
| } |
| |
| /* |
| * Checkup routine |
| * |
| * Data gathered from http://danher6.100webspace.net/ecc/#EFp_interactivo |
| * and double-checked using Pari-GP |
| */ |
| int ecp_self_test( int verbose ) |
| { |
| int ret = 0; |
| size_t i; |
| ecp_group grp; |
| ecp_point O, A, B, C, D, E, F, G, TMP; |
| ecp_point add_table[][3] = |
| { |
| {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_set_zero( &O ); |
| MPI_CHK( ecp_group_read_string( &grp, 10, "47", "4", "17", "42", "13" ) ); |
| MPI_CHK( ecp_point_read_string( &A, 10, "13", "0" ) ); |
| MPI_CHK( ecp_point_read_string( &B, 10, "14", "11" ) ); |
| MPI_CHK( ecp_point_read_string( &C, 10, "14", "36" ) ); |
| MPI_CHK( ecp_point_read_string( &D, 10, "37", "31" ) ); |
| MPI_CHK( ecp_point_read_string( &E, 10, "34", "14" ) ); |
| MPI_CHK( ecp_point_read_string( &F, 10, "45", "7" ) ); |
| MPI_CHK( ecp_point_read_string( &E, 10, "21", "32" ) ); |
| |
| if( verbose != 0 ) |
| printf( " ECP test #1 (ecp_add): " ); |
| |
| for( i = 0; i < sizeof( add_table ) / sizeof( add_table[0] ); i++ ) |
| { |
| MPI_CHK( ecp_add( &grp, &TMP, &add_table[i][0], &add_table[i][1] ) ); |
| if( ! ecp_point_eq( &TMP, &add_table[i][2] ) ) |
| { |
| if( verbose != 0 ) |
| printf(" failed (%zu)\n", i); |
| |
| return( 1 ); |
| } |
| } |
| |
| cleanup: |
| |
| if( ret != 0 && verbose != 0 ) |
| printf( "Unexpected error, return code = %08X\n", ret ); |
| |
| ecp_group_free( &grp ); |
| ecp_point_free( &O ); ecp_point_free( &A ); ecp_point_free( &B ); |
| ecp_point_free( &C ); ecp_point_free( &D ); ecp_point_free( &E ); |
| ecp_point_free( &F ); ecp_point_free( &G ); |
| |
| if( verbose != 0 ) |
| printf( "\n" ); |
| |
| return( ret ); |
| } |
| |
| #endif |
| |
| #endif |