import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.KeySpec;
import java.util.Arrays;import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;public class PasswordEncryptionService {public boolean authenticate(String attemptedPassword, byte[] encryptedPassword, byte[] salt)throws NoSuchAlgorithmException, InvalidKeySpecException {// Encrypt the clear-text password using the same salt that was used to// encrypt the original passwordbyte[] encryptedAttemptedPassword = getEncryptedPassword(attemptedPassword, salt);// Authentication succeeds if encrypted password that the user entered// is equal to the stored hashreturn Arrays.equals(encryptedPassword, encryptedAttemptedPassword);}public byte[] getEncryptedPassword(String password, byte[] salt)throws NoSuchAlgorithmException, InvalidKeySpecException {// PBKDF2 with SHA-1 as the hashing algorithm. Note that the NIST// specifically names SHA-1 as an acceptable hashing algorithm for PBKDF2String algorithm = "PBKDF2WithHmacSHA1";// SHA-1 generates 160 bit hashes, so that's what makes sense hereint derivedKeyLength = 160;// Pick an iteration count that works for you. The NIST recommends at// least 1,000 iterations:// http://csrc.nist.gov/publications/nistpubs/800-132/nist-sp800-132.pdf// iOS 4.x reportedly uses 10,000:// http://blog.crackpassword.com/2010/09/smartphone-forensics-cracking-blackberry-backup-passwords/int iterations = 20000;KeySpec spec = new PBEKeySpec(password.toCharArray(), salt, iterations, derivedKeyLength);SecretKeyFactory f = SecretKeyFactory.getInstance(algorithm);return f.generateSecret(spec).getEncoded();}public byte[] generateSalt() throws NoSuchAlgorithmException {// VERY important to use SecureRandom instead of just RandomSecureRandom random = SecureRandom.getInstance("SHA1PRNG");// Generate a 8 byte (64 bit) salt as recommended by RSA PKCS5byte[] salt = new byte[8];random.nextBytes(salt);return salt;}
}