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/*
* Diffie-Hellman-Merkle key exchange (prime generation)
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
#include "mbedtls/build_info.h"
#include "mbedtls/platform.h"
#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");
mbedtls_exit(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 acceptable 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;
int exit_code = MBEDTLS_EXIT_FAILURE;
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 < 2) {
usage:
mbedtls_printf(USAGE);
goto exit;
}
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_ext(&Q, 50, 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) {
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);
fclose(fout);
goto exit;
}
mbedtls_printf(" ok\n\n");
fclose(fout);
exit_code = MBEDTLS_EXIT_SUCCESS;
exit:
mbedtls_mpi_free(&G); mbedtls_mpi_free(&P); mbedtls_mpi_free(&Q);
mbedtls_ctr_drbg_free(&ctr_drbg);
mbedtls_entropy_free(&entropy);
mbedtls_exit(exit_code);
}
#endif /* MBEDTLS_BIGNUM_C && MBEDTLS_ENTROPY_C && MBEDTLS_FS_IO &&
MBEDTLS_CTR_DRBG_C && MBEDTLS_GENPRIME */
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