1/* Makes safe primes of a DR nature */
2#include <tommath.h>
3
4int sizes[] = { 1+256/DIGIT_BIT, 1+512/DIGIT_BIT, 1+768/DIGIT_BIT, 1+1024/DIGIT_BIT, 1+2048/DIGIT_BIT, 1+4096/DIGIT_BIT };
5int main(void)
6{
7   int res, x, y;
8   char buf[4096];
9   FILE *out;
10   mp_int a, b;
11
12   mp_init(&a);
13   mp_init(&b);
14
15   out = fopen("drprimes.txt", "w");
16   for (x = 0; x < (int)(sizeof(sizes)/sizeof(sizes[0])); x++) {
17   top:
18       printf("Seeking a %d-bit safe prime\n", sizes[x] * DIGIT_BIT);
19       mp_grow(&a, sizes[x]);
20       mp_zero(&a);
21       for (y = 1; y < sizes[x]; y++) {
22           a.dp[y] = MP_MASK;
23       }
24
25       /* make a DR modulus */
26       a.dp[0] = -1;
27       a.used = sizes[x];
28
29       /* now loop */
30       res = 0;
31       for (;;) {
32          a.dp[0] += 4;
33          if (a.dp[0] >= MP_MASK) break;
34          mp_prime_is_prime(&a, 1, &res);
35          if (res == 0) continue;
36          printf("."); fflush(stdout);
37          mp_sub_d(&a, 1, &b);
38          mp_div_2(&b, &b);
39          mp_prime_is_prime(&b, 3, &res);
40          if (res == 0) continue;
41          mp_prime_is_prime(&a, 3, &res);
42          if (res == 1) break;
43	}
44
45        if (res != 1) {
46           printf("Error not DR modulus\n"); sizes[x] += 1; goto top;
47        } else {
48           mp_toradix(&a, buf, 10);
49           printf("\n\np == %s\n\n", buf);
50           fprintf(out, "%d-bit prime:\np == %s\n\n", mp_count_bits(&a), buf); fflush(out);
51        }
52   }
53   fclose(out);
54
55   mp_clear(&a);
56   mp_clear(&b);
57
58   return 0;
59}
60
61
62/* $Source: /cvs/libtom/libtommath/etc/drprime.c,v $ */
63/* $Revision: 1.2 $ */
64/* $Date: 2005/05/05 14:38:47 $ */
65