pbkdf2.java

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package pbkdf2;

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;

/**
 *
 * @author nos
 */
public class Pbkdf2 {

    public static 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 password
        byte[] encryptedAttemptedPassword = getEncryptedPassword(attemptedPassword, salt);

        // Authentication succeeds if encrypted password that the user entered
        // is equal to the stored hash
        return Arrays.equals(encryptedPassword, encryptedAttemptedPassword);
    }

    public static 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 PBKDF2
        String algorithm = "PBKDF2WithHmacSHA1";
        // SHA-1 generates 160 bit hashes, so that's what makes sense here
        int derivedKeyLength = 512;
        // 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 = 4096;

        KeySpec spec = new PBEKeySpec(password.toCharArray(), salt, iterations, derivedKeyLength);

        SecretKeyFactory f = SecretKeyFactory.getInstance(algorithm);

        return f.generateSecret(spec).getEncoded();
    }

    public static byte[] generateSalt() throws NoSuchAlgorithmException {
        // VERY important to use SecureRandom instead of just Random
        SecureRandom random = SecureRandom.getInstance("SHA1PRNG");

        // Generate a 8 byte (64 bit) salt as recommended by RSA PKCS5
        byte[] salt = new byte[8];
        random.nextBytes(salt);

        return salt;
    }

    final protected static char[] hexArray = "0123456789ABCDEF".toCharArray();

    public static String bytesToHex(byte[] bytes) {
        char[] hexChars = new char[bytes.length * 2];
        for (int j = 0; j < bytes.length; j++) {
            int v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws Exception {
        // TODO code application logic here

        byte[] hash = getEncryptedPassword("password", "salt".getBytes());
        System.out.println(Arrays.toString(hash));
        System.out.println(bytesToHex(hash));

    }

}