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/*
* Example ECDSA program
*
* Copyright (C) 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.
*/
#if !defined(POLARSSL_CONFIG_FILE)
#include "polarssl/config.h"
#else
#include POLARSSL_CONFIG_FILE
#endif
#include "polarssl/entropy.h"
#include "polarssl/ctr_drbg.h"
#include "polarssl/ecdsa.h"
#include <string.h>
#include <stdio.h>
/*
* Uncomment to show key and signature details
*/
#define VERBOSE
/*
* Uncomment to force use of a specific curve
*/
#define ECPARAMS POLARSSL_ECP_DP_SECP192R1
#if !defined(ECPARAMS)
#define ECPARAMS ecp_curve_list()->grp_id
#endif
#if !defined(POLARSSL_ECDSA_C) || \
!defined(POLARSSL_ENTROPY_C) || !defined(POLARSSL_CTR_DRBG_C)
int main( int argc, char *argv[] )
{
((void) argc);
((void) argv);
printf("POLARSSL_ECDSA_C and/or "
"POLARSSL_ENTROPY_C and/or POLARSSL_CTR_DRBG_C not defined\n");
return( 0 );
}
#else
#if defined(VERBOSE)
static void dump_buf( const char *title, unsigned char *buf, size_t len )
{
size_t i;
printf( "%s", title );
for( i = 0; i < len; i++ )
printf("%c%c", "0123456789ABCDEF" [buf[i] / 16],
"0123456789ABCDEF" [buf[i] % 16] );
printf( "\n" );
}
static void dump_pubkey( const char *title, ecdsa_context *key )
{
unsigned char buf[300];
size_t len;
if( ecp_point_write_binary( &key->grp, &key->Q,
POLARSSL_ECP_PF_UNCOMPRESSED, &len, buf, sizeof buf ) != 0 )
{
printf("internal error\n");
return;
}
dump_buf( title, buf, len );
}
#else
#define dump_buf( a, b, c )
#define dump_pubkey( a, b )
#endif
int main( int argc, char *argv[] )
{
int ret;
ecdsa_context ctx_sign, ctx_verify;
entropy_context entropy;
ctr_drbg_context ctr_drbg;
unsigned char hash[] = "This should be the hash of a message.";
unsigned char sig[512];
size_t sig_len;
const char *pers = "ecdsa";
((void) argv);
ecdsa_init( &ctx_sign );
ecdsa_init( &ctx_verify );
memset(sig, 0, sizeof( sig ) );
ret = 1;
if( argc != 1 )
{
printf( "usage: ecdsa\n" );
#if defined(_WIN32)
printf( "\n" );
#endif
goto exit;
}
/*
* Generate a key pair for signing
*/
printf( "\n . Seeding the random number generator..." );
fflush( stdout );
entropy_init( &entropy );
if( ( ret = ctr_drbg_init( &ctr_drbg, entropy_func, &entropy,
(const unsigned char *) pers,
strlen( pers ) ) ) != 0 )
{
printf( " failed\n ! ctr_drbg_init returned %d\n", ret );
goto exit;
}
printf( " ok\n . Generating key pair..." );
fflush( stdout );
if( ( ret = ecdsa_genkey( &ctx_sign, ECPARAMS,
ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
printf( " failed\n ! ecdsa_genkey returned %d\n", ret );
goto exit;
}
printf( " ok (key size: %d bits)\n", (int) ctx_sign.grp.pbits );
dump_pubkey( " + Public key: ", &ctx_sign );
/*
* Sign some message hash
*/
printf( " . Signing message..." );
fflush( stdout );
if( ( ret = ecdsa_write_signature( &ctx_sign,
hash, sizeof( hash ),
sig, &sig_len,
ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
printf( " failed\n ! ecdsa_genkey returned %d\n", ret );
goto exit;
}
printf( " ok (signature length = %u)\n", (unsigned int) sig_len );
dump_buf( " + Hash: ", hash, sizeof hash );
dump_buf( " + Signature: ", sig, sig_len );
/*
* Signature is serialized as defined by RFC 4492 p. 20,
* but one can also access 'r' and 's' directly from the context
*/
#ifdef POLARSSL_FS_IO
mpi_write_file( " r = ", &ctx_sign.r, 16, NULL );
mpi_write_file( " s = ", &ctx_sign.s, 16, NULL );
#endif
/*
* Transfer public information to verifying context
*
* We could use the same context for verification and signatures, but we
* chose to use a new one in order to make it clear that the verifying
* context only needs the public key (Q), and not the private key (d).
*/
printf( " . Preparing verification context..." );
fflush( stdout );
if( ( ret = ecp_group_copy( &ctx_verify.grp, &ctx_sign.grp ) ) != 0 )
{
printf( " failed\n ! ecp_group_copy returned %d\n", ret );
goto exit;
}
if( ( ret = ecp_copy( &ctx_verify.Q, &ctx_sign.Q ) ) != 0 )
{
printf( " failed\n ! ecp_copy returned %d\n", ret );
goto exit;
}
ret = 0;
/*
* Verify signature
*/
printf( " ok\n . Verifying signature..." );
fflush( stdout );
if( ( ret = ecdsa_read_signature( &ctx_verify,
hash, sizeof( hash ),
sig, sig_len ) ) != 0 )
{
printf( " failed\n ! ecdsa_read_signature returned %d\n", ret );
goto exit;
}
printf( " ok\n" );
exit:
#if defined(_WIN32)
printf( " + Press Enter to exit this program.\n" );
fflush( stdout ); getchar();
#endif
ecdsa_free( &ctx_verify );
ecdsa_free( &ctx_sign );
ctr_drbg_free( &ctr_drbg );
entropy_free( &entropy );
return( ret );
}
#endif /* POLARSSL_ECDSA_C && POLARSSL_ENTROPY_C && POLARSSL_CTR_DRBG_C &&
ECPARAMS */