<code lang="Java">
/**
 * FastExpon is a fast computational algorithm for computing large exponents. x^e % m
 * This algorithm was used for a cryptography course dealing with RSA.
 * Feel free to slice it up for yourself. :)
 * @author Alan Lambkin
 * @version 1.0 September 2006
 */

public class FastExpon
{
	public long y = 1;

	/**
	 * Performs the calculation...
	 * While the exponent is not zero:
	 * If the exponent is even, square the base, mod m, and divide the exponent by 2.
	 * If the exponent is odd, mulitply the base times y (initially set to 1) mod m,
	 * now place that value into y, and subtract 1 from the exponent.
	 * @parm 	x	the base
	 * @parm 	e	the exponent
	 * @parm 	m	the mod
	 * @return 	The answer, x raised to e, mod m.
	 */
	public long fex(long x, long e, long m)
	{
		while (e != 0)
		{
			if (e%2==0)
			{
				x=x*x%m;
				e=e/2;
			}
			else
			{
				y=x*y%m;
				e=e-1;
			}
		}
		return y;
	}

	/**
	 * Just a simple main program so I can test before posting.
	 * Prints out the answer.
	 */
	public static void main(String[] args)
	{
		long x = 6916502;
		long e = 2773637;
		long m = 8326363;
		FastExpon f = new FastExpon();
		System.out.println(x + " raised to the " + e + " power, mod " + m + " = " + f.fex(x,e,m));
	}
}
</code>