michael@0: /*
michael@0:  *  exptmod.c
michael@0:  *
michael@0:  * Command line tool to perform modular exponentiation on arbitrary
michael@0:  * precision integers.
michael@0:  *
michael@0:  * This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include <stdio.h>
michael@0: #include <stdlib.h>
michael@0: #include <string.h>
michael@0: 
michael@0: #include "mpi.h"
michael@0: 
michael@0: int main(int argc, char *argv[])
michael@0: {
michael@0:   mp_int  a, b, m;
michael@0:   mp_err  res;
michael@0:   char   *str;
michael@0:   int     len, rval = 0;
michael@0: 
michael@0:   if(argc < 3) {
michael@0:     fprintf(stderr, "Usage: %s <a> <b> <m>\n", argv[0]);
michael@0:     return 1;
michael@0:   }
michael@0: 
michael@0:   mp_init(&a); mp_init(&b); mp_init(&m);
michael@0:   mp_read_radix(&a, argv[1], 10);
michael@0:   mp_read_radix(&b, argv[2], 10);
michael@0:   mp_read_radix(&m, argv[3], 10);
michael@0: 
michael@0:   if((res = mp_exptmod(&a, &b, &m, &a)) != MP_OKAY) {
michael@0:     fprintf(stderr, "%s: error: %s\n", argv[0], mp_strerror(res));
michael@0:     rval = 1;
michael@0:   } else {
michael@0:     len = mp_radix_size(&a, 10);
michael@0:     str = calloc(len, sizeof(char));
michael@0:     mp_toradix(&a, str, 10);
michael@0: 
michael@0:     printf("%s\n", str);
michael@0: 
michael@0:     free(str);
michael@0:   }
michael@0: 
michael@0:   mp_clear(&a); mp_clear(&b); mp_clear(&m);
michael@0: 
michael@0:   return rval;
michael@0: }