| /* |
| * Elliptic curve DSA |
| * |
| * Copyright (C) 2006-2013, 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 |
| */ |
| |
| #include "polarssl/config.h" |
| |
| #if defined(POLARSSL_ECDSA_C) |
| |
| #include "polarssl/ecdsa.h" |
| |
| /* |
| * Compute ECDSA signature of a hashed message (SEC1 4.1.3) |
| * Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message) |
| */ |
| int ecdsa_sign( const ecp_group *grp, mpi *r, mpi *s, |
| const mpi *d, const unsigned char *buf, size_t blen, |
| int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) |
| { |
| int ret, key_tries, sign_tries; |
| size_t n_size; |
| ecp_point R; |
| mpi k, e; |
| |
| ecp_point_init( &R ); |
| mpi_init( &k ); |
| mpi_init( &e ); |
| |
| sign_tries = 0; |
| do |
| { |
| /* |
| * Steps 1-3: generate a suitable ephemeral keypair |
| */ |
| key_tries = 0; |
| do |
| { |
| MPI_CHK( ecp_gen_keypair( grp, &k, &R, f_rng, p_rng ) ); |
| MPI_CHK( mpi_copy( r, &R.X ) ); |
| |
| if( key_tries++ > 10 ) |
| return( POLARSSL_ERR_ECP_GENERIC ); |
| } |
| while( mpi_cmp_int( r, 0 ) == 0 ); |
| |
| /* |
| * Step 5: derive MPI from hashed message |
| */ |
| n_size = (grp->nbits + 7) / 8; |
| MPI_CHK( mpi_read_binary( &e, buf, blen > n_size ? n_size : blen ) ); |
| |
| /* |
| * Step 6: compute s = (e + r * d) / k mod n |
| */ |
| MPI_CHK( mpi_mul_mpi( s, r, d ) ); |
| MPI_CHK( mpi_add_mpi( &e, &e, s ) ); |
| MPI_CHK( mpi_inv_mod( s, &k, &grp->N ) ); |
| MPI_CHK( mpi_mul_mpi( s, s, &e ) ); |
| MPI_CHK( mpi_mod_mpi( s, s, &grp->N ) ); |
| |
| if( sign_tries++ > 10 ) |
| return( POLARSSL_ERR_ECP_GENERIC ); |
| } |
| while( mpi_cmp_int( s, 0 ) == 0 ); |
| |
| cleanup: |
| ecp_point_free( &R ); |
| mpi_free( &k ); |
| mpi_free( &e ); |
| |
| return( ret ); |
| } |
| |
| #if defined(POLARSSL_SELF_TEST) |
| |
| /* |
| * Checkup routine |
| */ |
| int ecdsa_self_test( int verbose ) |
| { |
| return( verbose++ ); |
| } |
| |
| #endif |
| |
| #endif /* defined(POLARSSL_ECDSA_C) */ |