Class ToolPbkdf2

security/src/main/java/pro/tools/security/ToolPbkdf2.java:26–81

类名称：PBKDF2 修改备注： 1.当增加一个用户的时候，调用generateSalt()生成盐，然后调用getEncryptedPassword(),同时存储盐和密文。 再次强调，不要存储明文密码，不要存储明文密码，因为没必要！不要担心将盐和密文存储在同一张表中，上面已经说过了，这个无关紧要。 2.当认证用户的时候，从数据库中取出盐和密文，将他们和明文密码同时传给authenticate()，根据返回结果判断是否认证成功。 3.当用户修改密码的时候，仍然可以使用原来的盐，只需要调用getEncryptedPassword()方法重新生成密文就可以了。 @a

 * @author SeanDragon
 */
public final class ToolPbkdf2 {
    private ToolPbkdf2() {
        throw new UnsupportedOperationException("我是工具类，别初始化我。。。");
    }

    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 = 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 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;
    }

}