mp_result find_strong_prime(mp_int seed, FILE *fb)
{
mp_result res;
mpz_t t;
mp_int_init(&t);
for(;;) {
if ((res = find_prime(seed, fb)) != MP_TRUE)
break;
if ((res = mp_int_copy(seed, &t)) != MP_OK)
break;
if ((res = mp_int_mul_pow2(&t, 1, &t)) != MP_OK ||
(res = mp_int_add_value(&t, 1, &t)) != MP_OK)
break;
if ((res = mp_int_is_prime(&t)) == MP_TRUE) {
if (fb != NULL)
fputc('!', fb);
res = mp_int_copy(&t, seed);
break;
}
else if (res != MP_FALSE)
break;
if (fb != NULL)
fputc('x', fb);
if ((res = mp_int_add_value(seed, 2, seed)) != MP_OK)
break;
}
mp_int_clear(&t);
return res;
}
/* Find the first apparent prime in ascending order from z */
mp_result mp_int_find_prime(mp_int z)
{
mp_result res;
if(mp_int_is_even(z) && ((res = mp_int_add_value(z, 1, z)) != MP_OK))
return res;
while((res = mp_int_is_prime(z)) == MP_FALSE) {
if((res = mp_int_add_value(z, 2, z)) != MP_OK)
break;
}
return res;
}
mp_result find_prime(mp_int seed, FILE *fb)
{
mp_result res;
int count = 0;
if(mp_int_is_even(seed))
if((res = mp_int_add_value(seed, 1, seed)) != MP_OK)
return res;
while((res = mp_int_is_prime(seed)) == MP_FALSE) {
++count;
if(fb != NULL && (count % 50) == 0)
fputc('.', fb);
if((res = mp_int_add_value(seed, 2, seed)) != MP_OK)
return res;
}
if(res == MP_TRUE && fb != NULL)
fputc('+', fb);
return res;
}
