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  /*
   * Password Hashing With PBKDF2 (http://crackstation.net/hashing-security.htm).
   * Copyright (c) 2013, Taylor Hornby
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are met:
   *
   * 1. Redistributions of source code must retain the above copyright notice,
  * this list of conditions and the following disclaimer.
  *
  * 2. Redistributions in binary form must reproduce the above copyright notice,
  * this list of conditions and the following disclaimer in the documentation
  * and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */
 
 package nw.commons;
 
 
 /*
  * PBKDF2 salted password hashing.
  * Author: havoc AT defuse.ca
  * www: http://crackstation.net/hashing-security.htm
  */
The Class PasswordHash.
 
 public class PasswordHash {

The Constant PBKDF2_ALGORITHM.
 
 	public static final String PBKDF2_ALGORITHM = "PBKDF2WithHmacSHA1";
 
 	// The following constants may be changed without breaking existing hashes.
 	
The Constant SALT_BYTE_SIZE.
 
 	public static final int SALT_BYTE_SIZE = 24;

The Constant HASH_BYTE_SIZE.
 
 	public static final int HASH_BYTE_SIZE = 24;

The Constant PBKDF2_ITERATIONS.
 
 	public static final int PBKDF2_ITERATIONS = 1000;

The Constant ITERATION_INDEX.
 
 	public static final int ITERATION_INDEX = 0;

The Constant SALT_INDEX.
 
 	public static final int SALT_INDEX = 1;

The Constant PBKDF2_INDEX.
 
 	public static final int PBKDF2_INDEX = 2;

Returns a salted PBKDF2 hash of the password.

Parameters:
password the password
Returns:
a salted PBKDF2 hash of the password
Throws:
java.security.NoSuchAlgorithmException the no such algorithm exception
java.security.spec.InvalidKeySpecException the invalid key spec exception
 
 	public static String createHash(String password)
 		return createHash(password.toCharArray());
 	}

Returns a salted PBKDF2 hash of the password.

Parameters:
password the password
Returns:
a salted PBKDF2 hash of the password
Throws:
java.security.NoSuchAlgorithmException the no such algorithm exception
java.security.spec.InvalidKeySpecException the invalid key spec exception
 
 	public static String createHash(char[] password)
 		// Generate a random salt
		SecureRandom random = new SecureRandom();
		byte[] salt = new byte[];
		random.nextBytes(salt);
		// Hash the password
		byte[] hash = pbkdf2(passwordsalt);
		// format iterations:salt:hash
		return  + ":" + toHex(salt) + ":" + toHex(hash);
	}

Validates a password using a hash.

Parameters:
password the password
correctHash the correct hash
Returns:
true if the password is correct, false if not
Throws:
java.security.NoSuchAlgorithmException the no such algorithm exception
java.security.spec.InvalidKeySpecException the invalid key spec exception
	public static boolean validatePassword(String passwordString correctHash)
		return validatePassword(password.toCharArray(), correctHash);
	}

Validates a password using a hash.

Parameters:
password the password
correctHash the correct hash
Returns:
true if the password is correct, false if not
Throws:
java.security.NoSuchAlgorithmException the no such algorithm exception
java.security.spec.InvalidKeySpecException the invalid key spec exception
	public static boolean validatePassword(char[] passwordString correctHash)
		// Decode the hash into its parameters
		String[] params = correctHash.split(":");
		int iterations = Integer.parseInt(params[]);
		byte[] salt = fromHex(params[]);
		byte[] hash = fromHex(params[]);
		// Compute the hash of the provided password, using the same salt,
		// iteration count, and hash length
		byte[] testHash = pbkdf2(passwordsaltiterationshash.length);
		// Compare the hashes in constant time. The password is correct if
		// both hashes match.
		return slowEquals(hashtestHash);
	}

Compares two byte arrays in length-constant time. This comparison method is used so that password hashes cannot be extracted from an on-line system using a timing attack and then attacked off-line.

Parameters:
a the a
b the b
Returns:
true if both byte arrays are the same, false if not
	private static boolean slowEquals(byte[] abyte[] b) {
		int diff = a.length ^ b.length;
		for (int i = 0; i < a.length && i < b.lengthi++)
			diff |= a[i] ^ b[i];
		return diff == 0;
	}

Computes the PBKDF2 hash of a password.

Parameters:
password the password
salt the salt
iterations the iterations
bytes the bytes
Returns:
the PBDKF2 hash of the password
Throws:
java.security.NoSuchAlgorithmException the no such algorithm exception
java.security.spec.InvalidKeySpecException the invalid key spec exception
	private static byte[] pbkdf2(char[] passwordbyte[] saltint iterations,
		PBEKeySpec spec = new PBEKeySpec(passwordsaltiterationsbytes * 8);
		SecretKeyFactory skf = SecretKeyFactory.getInstance();
		return skf.generateSecret(spec).getEncoded();
	}

Converts a string of hexadecimal characters into a byte array.

Parameters:
hex the hex
Returns:
the hex string decoded into a byte array
	private static byte[] fromHex(String hex) {
		byte[] binary = new byte[hex.length() / 2];
		for (int i = 0; i < binary.lengthi++) {
			binary[i] = (byte) Integer.parseInt(
					hex.substring(2 * i, 2 * i + 2), 16);
		}
		return binary;
	}

Converts a byte array into a hexadecimal string.

Parameters:
array the array
Returns:
a length*2 character string encoding the byte array
	private static String toHex(byte[] array) {
		BigInteger bi = new BigInteger(1, array);
		String hex = bi.toString(16);
		int paddingLength = (array.length * 2) - hex.length();
		if (paddingLength > 0)
			return String.format("%0" + paddingLength + "d", 0) + hex;
		else
			return hex;
	}

Tests the basic functionality of the PasswordHash class.

Parameters:
args the arguments
	public static void main(String[] args) {
		try {
			// Print out 10 hashes
			for (int i = 0; i < 10; i++)
				..println(PasswordHash.createHash("p\r\nassw0Rd!"));
			// Test password validation
			boolean failure = false;
			..println("Running tests...");
			for (int i = 0; i < 100; i++) {
				String password = "" + i;
				String hash = createHash(password);
				String secondHash = createHash(password);
				if (hash.equals(secondHash)) {
					..println("FAILURE: TWO HASHES ARE EQUAL!");
					failure = true;
				}
				String wrongPassword = "" + (i + 1);
				if (validatePassword(wrongPasswordhash)) {
					..println("FAILURE: WRONG PASSWORD ACCEPTED!");
					failure = true;
				}
				if (!validatePassword(passwordhash)) {
					..println("FAILURE: GOOD PASSWORD NOT ACCEPTED!");
					failure = true;
				}
			}
			if (failure)
				..println("TESTS FAILED!");
			else
				..println("TESTS PASSED!");
catch (Exception ex) {
			..println("ERROR: " + ex);
		}
	}
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