Password.java

package com.entityreborn.socpuppet.util;

/**
 * Taken from http://stackoverflow.com/a/11038230/1511299
 */
import java.security.SecureRandom;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import org.apache.commons.codec.binary.Base64;

public class Password {
    // The higher the number of iterations the more 
    // expensive computing the hash is for us
    // and also for a brute force attack.
    private static final int iterations = 10*1024;
    private static final int saltLen = 32;
    private static final int desiredKeyLen = 256;

    /** Computes a salted PBKDF2 hash of given plaintext password
        suitable for storing in a database. 
        Empty passwords are not supported.
     * @param password
     * @return 
     * @throws java.lang.Exception
     */
    public static String getSaltedHash(String password) throws Exception {
        byte[] salt = SecureRandom.getInstance("SHA1PRNG").generateSeed(saltLen);
        // store the salt with the password
        return Base64.encodeBase64String(salt) + "$" + hash(password, salt);
    }

    /** Checks whether given plaintext password corresponds 
        to a stored salted hash of the password.
     * @param password
     * @param stored
     * @throws java.lang.Exception 
     */
    public static boolean check(String password, String stored) throws Exception {
        String[] saltAndPass = stored.split("\\$");
        if (saltAndPass.length != 2)
            return false;
        String hashOfInput = hash(password, Base64.decodeBase64(saltAndPass[0]));
        return hashOfInput.equals(saltAndPass[1]);
    }

    // using PBKDF2 from Sun, an alternative is https://github.com/wg/scrypt
    // cf. http://www.unlimitednovelty.com/2012/03/dont-use-bcrypt.html
    private static String hash(String password, byte[] salt) throws Exception {
        if (password == null || password.length() == 0) {
            throw new IllegalArgumentException("Empty passwords are not supported.");
        }
        
        SecretKeyFactory f = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");
        SecretKey key = f.generateSecret(new PBEKeySpec(
                password.toCharArray(), salt, iterations, desiredKeyLen)
        );
        
        return Base64.encodeBase64String(key.getEncoded());
    }
}