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comparison etc/drprime.c @ 1:22d5cf7d4b1a libtommath

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Renaming branch
author Matt Johnston <matt@ucc.asn.au>
date Mon, 31 May 2004 18:23:46 +0000
parents
children 97db060d0ef5
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-1:000000000000 1:22d5cf7d4b1a
1 /* Makes safe primes of a DR nature */
2 #include <tommath.h>
3
4 int 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 };
5 int 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