/* Miller-Rabin test for primality. Slow. */
public static bool prime(FF p, RAND rng)
{
int i, j, s = 0, n = p.length;
bool loop;
FF d = new FF(n);
FF x = new FF(n);
FF unity = new FF(n);
FF nm1 = new FF(n);
int sf = 4849845; // 3*5*.. *19
p.norm();
if (p.cfactor(sf))
{
return(false);
}
unity.one();
nm1.copy(p);
nm1.sub(unity);
nm1.norm();
d.copy(nm1);
while (d.parity() == 0)
{
d.shr();
s++;
}
if (s == 0)
{
return(false);
}
for (i = 0; i < 10; i++)
{
x.randomnum(p, rng);
x.pow(d, p);
if (comp(x, unity) == 0 || comp(x, nm1) == 0)
{
continue;
}
loop = false;
for (j = 1; j < s; j++)
{
x.power(2, p);
if (comp(x, unity) == 0)
{
return(false);
}
if (comp(x, nm1) == 0)
{
loop = true;
break;
}
}
if (loop)
{
continue;
}
return(false);
}
return(true);
}