// This function is called for all k trials.
// It returns false if n is composite and
// returns false if n is probably prime.
// d is an odd number such that d*2<sup>r</sup>
// = n-1 for some r >= 1
private bool MillerTest(int d, int n)
{
// Pick a random number in [2..n-2]
// Corner cases make sure that n > 4
int a = 2 + (int)(rng.Next() % (n - 4));
// Compute a^d % n
int x = ComputationUtils.Power(a, d, n);
if (x == 1 || x == n - 1)
{
return(true);
}
// Keep squaring x while one of the
// following doesn't happen
// (i) d does not reach n-1
// (ii) (x^2) % n is not 1
// (iii) (x^2) % n is not n-1
while (d != n - 1)
{
x = (x * x) % n;
d *= 2;
if (x == 1)
{
return(false);
}
if (x == n - 1)
{
return(true);
}
}
return(false);
}
public bool IsPrime(int n)
{
// If it is composite and satisfy Fermat criterion
if (a > 1 && IsComposite(n) &&
ComputationUtils.Power(a, n - 1, n) == 1)
{
return(true);
}
// Else return 0
return(false);
}
