power_mod_q

Get a number raised to a power mod q.

function power_mod_q(x,n,q)
{
   //Logic
  if(n === 0)
      return 1;
  if(n % 2 === 0)
      return power_mod_q((x * x) % q, n / 2, q);
  else
      return (x * power_mod_q((x * x) % q, n / 2, q)) % q;
}