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/*
* Diffie-Hellman-Merkle key exchange (prime generation)
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#define mbedtls_printf printf
#endif
#if !defined(MBEDTLS_BIGNUM_C) || !defined(MBEDTLS_ENTROPY_C) || \
!defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
!defined(MBEDTLS_GENPRIME)
int main( void )
{
mbedtls_printf("MBEDTLS_BIGNUM_C and/or MBEDTLS_ENTROPY_C and/or "
"MBEDTLS_FS_IO and/or MBEDTLS_CTR_DRBG_C and/or "
"MBEDTLS_GENPRIME not defined.\n");
return( 0 );
}
#else
#include "mbedtls/bignum.h"
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include <stdio.h>
#include <string.h>
#define USAGE \
"\n usage: dh_genprime param=<>...\n" \
"\n acceprable parameters:\n" \
" bits=%%d default: 2048\n"
#define DFL_BITS 2048
/*
* Note: G = 4 is always a quadratic residue mod P,
* so it is a generator of order Q (with P = 2*Q+1).
*/
#define GENERATOR "4"
int main( int argc, char **argv )
{
int ret = 1;
mbedtls_mpi G, P, Q;
mbedtls_entropy_context entropy;
mbedtls_ctr_drbg_context ctr_drbg;
const char *pers = "dh_genprime";
FILE *fout;
int nbits = DFL_BITS;
int i;
char *p, *q;
mbedtls_mpi_init( &G ); mbedtls_mpi_init( &P ); mbedtls_mpi_init( &Q );
mbedtls_ctr_drbg_init( &ctr_drbg );
mbedtls_entropy_init( &entropy );
if( argc == 0 )
{
usage:
mbedtls_printf( USAGE );
return( 1 );
}
for( i = 1; i < argc; i++ )
{
p = argv[i];
if( ( q = strchr( p, '=' ) ) == NULL )
goto usage;
*q++ = '\0';
if( strcmp( p, "bits" ) == 0 )
{
nbits = atoi( q );
if( nbits < 0 || nbits > MBEDTLS_MPI_MAX_BITS )
goto usage;
}
else
goto usage;
}
if( ( ret = mbedtls_mpi_read_string( &G, 10, GENERATOR ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_read_string returned %d\n", ret );
goto exit;
}
mbedtls_printf( " ! Generating large primes may take minutes!\n" );
mbedtls_printf( "\n . Seeding the random number generator..." );
fflush( stdout );
if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
(const unsigned char *) pers,
strlen( pers ) ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
goto exit;
}
mbedtls_printf( " ok\n . Generating the modulus, please wait..." );
fflush( stdout );
/*
* This can take a long time...
*/
if( ( ret = mbedtls_mpi_gen_prime( &P, nbits, 1,
mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_gen_prime returned %d\n\n", ret );
goto exit;
}
mbedtls_printf( " ok\n . Verifying that Q = (P-1)/2 is prime..." );
fflush( stdout );
if( ( ret = mbedtls_mpi_sub_int( &Q, &P, 1 ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_sub_int returned %d\n\n", ret );
goto exit;
}
if( ( ret = mbedtls_mpi_div_int( &Q, NULL, &Q, 2 ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_div_int returned %d\n\n", ret );
goto exit;
}
if( ( ret = mbedtls_mpi_is_prime( &Q, mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_is_prime returned %d\n\n", ret );
goto exit;
}
mbedtls_printf( " ok\n . Exporting the value in dh_prime.txt..." );
fflush( stdout );
if( ( fout = fopen( "dh_prime.txt", "wb+" ) ) == NULL )
{
ret = 1;
mbedtls_printf( " failed\n ! Could not create dh_prime.txt\n\n" );
goto exit;
}
if( ( ret = mbedtls_mpi_write_file( "P = ", &P, 16, fout ) != 0 ) ||
( ret = mbedtls_mpi_write_file( "G = ", &G, 16, fout ) != 0 ) )
{
mbedtls_printf( " failed\n ! mbedtls_mpi_write_file returned %d\n\n", ret );
goto exit;
}
mbedtls_printf( " ok\n\n" );
fclose( fout );
exit:
mbedtls_mpi_free( &G ); mbedtls_mpi_free( &P ); mbedtls_mpi_free( &Q );
mbedtls_ctr_drbg_free( &ctr_drbg );
mbedtls_entropy_free( &entropy );
#if defined(_WIN32)
mbedtls_printf( " Press Enter to exit this program.\n" );
fflush( stdout ); getchar();
#endif
return( ret );
}
#endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_FS_IO &&
MBEDTLS_CTR_DRBG_C && MBEDTLS_GENPRIME */
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