cs456-a3/keygen.c

#include "randsource.h"
#include "sgprime.h"

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

#define RAND_SIZE 512
#define CHUNK_SIZE 1

int main(int argc, char **argv)
{
  unsigned int threads;
  unsigned int bits;
  FILE *keyoutf;

  if (argc < 3 || argc > 4)
  {
    printf("Usage: %s <bits> <output file> [threads]\n", argv[0]);
    return 0;
  }

  if (argc == 3)
  {
    threads = 0;
  } else
  {
    if (1 != sscanf(argv[3], "%u", &threads) || threads == 0)
    {
      printf("number of threads must be a positive integer\n");
      return 0;
    }

  }

  if (1 != sscanf(argv[1], "%u", &bits) || bits == 0)
  {
    printf("number of bits must be a positive integer\n");
    return 0;
  }

  keyoutf = fopen(argv[2], "w");
  if (keyoutf == NULL)
  {
    perror("could not open key out file: ");
    return 1;
  }

  printf("Key Generation Tool\n");

  printf("generating a key with %u bits ...\n", bits);

  fflush(stdout);

  mpz_t l, p, seed, rc, g, t;
  mpz_init(p);
  mpz_init(l);
  mpz_init(g);
  mpz_init(t);
  mpz_init(seed);

  mpz_set_ui(l, 0);
  mpz_setbit(l, bits);

  unsigned long int offset, primorial;
  void *difflist = make_difflist(l, &offset, &primorial);

  gmp_randstate_t rs;
  gmp_randinit_default(rs);

  char *randbuff = malloc(RAND_SIZE);
  if (fill_random(randbuff, RAND_SIZE))
  {
    perror("unable to read randomness source: ");
    return 2;
  }

  mpz_import(seed, RAND_SIZE, 1, 1, 0, 0, randbuff);
  gmp_randseed(rs, seed);

  free(randbuff);

  mpz_urandomb(p, rs, bits);
  mpz_setbit(p, bits);

  printf("generating safe prime ... ");
  fflush(stdout);
  get_sg_prime(difflist, offset, primorial, p, threads, bits + 4, CHUNK_SIZE);
  printf("done\n");
  fflush(stdout);

  destroy_difflist(difflist);

  mpz_mul_ui(l, p, 2);

  rc[0] = seed[0]; // Moving variable names -- not portable
  mpz_set(rc, l);

  mpz_add_ui(l, l, 1);

  printf("finding a generator ... ");
  fflush(stdout);
  while (1)
  {
    mpz_urandomm(g, rs, rc);
    mpz_add_ui(rc, rc, 1);
    mpz_powm_ui(t, g, 2, l);
    if (mpz_cmp_ui(g, 1) != 0)
    {
      mpz_powm(t, g, p, l);
      if (mpz_cmp_ui(g, 1) != 0)
        break;
    }
  }
  printf("done\n");
  fflush(stdout);

  printf("creating a secret exponent ... ");
  fflush(stdout);
  mpz_urandomm(p, rs, l);
  printf("done\n");
  fflush(stdout);

  printf("computing public point ... ");
  fflush(stdout);
  mpz_powm(rc, g, p, l);
  printf("done\n");
  fflush(stdout);

  gmp_randclear(rs);

  gmp_fprintf(keyoutf, "m=%Zd\ng=%Zd\nx=%Zd\np=%Zd\n", l, g, p, rc);

  mpz_clear(seed);
  mpz_clear(p);
  mpz_clear(l);
  mpz_clear(g);
  mpz_clear(t);

  fclose(keyoutf);
}