### view libtommath/etc/2kprime.c @ 389:5ff8218bcee9

author Matt Johnston Thu, 11 Jan 2007 03:14:55 +0000 eed26cff980b 60fc6476e044
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```/* Makes safe primes of a 2k nature */
#include <tommath.h>
#include <time.h>

int sizes[] = {256, 512, 768, 1024, 1536, 2048, 3072, 4096};

int main(void)
{
char buf[2000];
int x, y;
mp_int q, p;
FILE *out;
clock_t t1;
mp_digit z;

mp_init_multi(&q, &p, NULL);

out = fopen("2kprime.1", "w");
for (x = 0; x < (int)(sizeof(sizes) / sizeof(sizes[0])); x++) {
top:
mp_2expt(&q, sizes[x]);
z = -3;

t1 = clock();
for(;;) {
mp_sub_d(&q, 4, &q);
z += 4;

printf("No primes of size %d found\n", sizes[x]);
break;
}

if (clock() - t1 > CLOCKS_PER_SEC) {
printf("."); fflush(stdout);
//            sleep((clock() - t1 + CLOCKS_PER_SEC/2)/CLOCKS_PER_SEC);
t1 = clock();
}

/* quick test on q */
mp_prime_is_prime(&q, 1, &y);
if (y == 0) {
continue;
}

/* find (q-1)/2 */
mp_sub_d(&q, 1, &p);
mp_div_2(&p, &p);
mp_prime_is_prime(&p, 3, &y);
if (y == 0) {
continue;
}

/* test on q */
mp_prime_is_prime(&q, 3, &y);
if (y == 0) {
continue;
}

break;
}

if (y == 0) {
++sizes[x];
goto top;
}

printf("\n\n%d-bits (k = %lu) = %s\n", sizes[x], z, buf);
fprintf(out, "%d-bits (k = %lu) = %s\n", sizes[x], z, buf); fflush(out);
}

return 0;
}

/* \$Source: /cvs/libtom/libtommath/etc/2kprime.c,v \$ */
/* \$Revision: 1.2 \$ */
/* \$Date: 2005/05/05 14:38:47 \$ */
```