/****************************************************************************** * Compilation: javac PollardRho.java * Execution: java PollardRho N * * Factor N using the Pollard-Rho method. * * % java PollardRho 44343535354351600000003434353 * 149 * 329569479697 * 903019357561501 * ******************************************************************************/ import java.math.BigInteger; import java.security.SecureRandom; class PollardRho { private final static BigInteger ZERO = new BigInteger("0"); private final static BigInteger ONE = new BigInteger("1"); private final static BigInteger TWO = new BigInteger("2"); private final static SecureRandom random = new SecureRandom(); public static BigInteger rho(BigInteger N) { BigInteger divisor; BigInteger c = new BigInteger(N.bitLength(), random); BigInteger x = new BigInteger(N.bitLength(), random); BigInteger xx = x; // check divisibility by 2 if (N.mod(TWO).compareTo(ZERO) == 0) return TWO; do { x = x.multiply(x).mod(N).add(c).mod(N); xx = xx.multiply(xx).mod(N).add(c).mod(N); xx = xx.multiply(xx).mod(N).add(c).mod(N); divisor = x.subtract(xx).gcd(N); } while((divisor.compareTo(ONE)) == 0); return divisor; } public static void factor(BigInteger N) { if (N.compareTo(ONE) == 0) return; if (N.isProbablePrime(20)) { StdOut.println(N); return; } BigInteger divisor = rho(N); factor(divisor); factor(N.divide(divisor)); } public static void main(String[] args) { BigInteger N = new BigInteger(args[0]); factor(N); } }