Java，PHP和Objective-C中的pbkdf2 pkcs5兼容哈希

Question

I'm developing an app that requires pbkdf2 pkcs5 for password hashing. I think I have some working code in PHP & Java but I'm not sure why they are producing different results.

Here are the code.

Php code:

function hash_password($password, $salt, $user_id, $iterations) {
    $user_id = (string) $user_id;
    $raw_pass = $salt . $user_id . $password;

    $hash = hash_pbkdf2("sha512", $raw_pass, $salt, $iterations, 64, false);

    return $hash;
}

echo hash_password("password", $salt, 2058, 1);
echo PHP_EOL;

Java code:

import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import java.nio.charset.StandardCharsets;
import java.lang.RuntimeException;
import java.security.NoSuchAlgorithmException;
import java.security.spec.InvalidKeySpecException;
import java.math.BigInteger;
import javax.xml.bind.DatatypeConverter;


public final class Testing {
    private static String mSalt = "fd6c3dc0165dc420b4e9225bc9bee9684387e9621b2e2c00cfffebf1ec7c30b4";

    private static String hashPassword(String password, String salt, int userId, int iterations) throws RuntimeException {
        String uid = String.valueOf(userId);
        StringBuilder pwBuilder = new StringBuilder(salt);
        pwBuilder.append(uid);
        pwBuilder.append(password);
        String rawPass = pwBuilder.toString();

        try {
            SecretKeyFactory skf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA512");
            PBEKeySpec spec = new PBEKeySpec(password.toCharArray(), mSalt.getBytes(), iterations, 256);
            byte[] result = skf.generateSecret(spec).getEncoded();

            StringBuilder hashBuilder = new StringBuilder(result.length * 2);

            for (byte r : result) {
                hashBuilder.append(String.format("%02x", r));
            }

            return hashBuilder.toString();
       } catch (NoSuchAlgorithmException | InvalidKeySpecException e) {
            throw new RuntimeException( e );
       }
    }

    public static void main(String[] args) {
        System.out.println(hashPassword("password", mSalt, 2058, 1000000));
        System.out.println("\n");
    }
}

Php output is: 3754036ea2f37af8160e45d15c2e4d6597157ead118f060e76152c0813f806e8
Java output is: 8b135bb19263677b70f1d5cbda5a23bc16df38e5e1a624c6df9a462975cac899

Can you recommend a library or a gist somewhere that has both compatible implementation?

Answer 1

You have two issues with your existing code:

1. Use the same number of iterations.

2. Use the same concatenated password.

In PHP:

Use

var_dump(hash_password("password", $salt, 2058, ));

instead of

var_dump(hash_password("password", $salt, 2058, ));

In Java:

Use

PBEKeySpec spec = new PBEKeySpec(.toCharArray(), mSalt.getBytes(), iterations, 256);

instead of

PBEKeySpec spec = new PBEKeySpec(.toCharArray(), mSalt.getBytes(), iterations, 256);

After you've made those changes, both will produce the same result:

424a0b30ea0cdef2ff0185f49ce67ee44273ce7e41026044d527c85550b3a207

---

Other issues:

• Never use String#getBytes without a specific character set. Otherwise, the system default will be used which can be different in different JVM's.

• If you're using PBKDF2 to hash passwords, then you will need to compare two hashes when verifying the re-entered password. This requires a constant-time comparison function to prevent timing-based attacks.