decrypting aes-gcm encrypted with java using openssl

Question

I have the following code in Java:

public static void deriveKeyAndIV(String password)
            throws Exception
    {
        SecureRandom random = new SecureRandom();
        if (salt == null)
        {
            salt = new byte[HASH_BYTE_SIZE / 8]; // use salt size at least as long as hash
            random.nextBytes(salt);
        }
        if (ivBytes == null)
        {
            ivBytes = new byte[HASH_BYTE_SIZE / 8];
            random.nextBytes(ivBytes);
        }

        PBEKeySpec spec = new PBEKeySpec(password.toCharArray(), salt, PBKDF2_ITERATIONS, HASH_BYTE_SIZE);
        SecretKeyFactory skf = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256");
        keyBytes = skf.generateSecret(spec).getEncoded();
    }
public static byte[] encrypt(byte[] message) 
            throws Exception
    {
        // wrap key data in Key/IV specs to pass to cipher
        SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");
        //IvParameterSpec ivSpec = new IvParameterSpec(ivBytes);
        // create the cipher with the algorithm you choose
        // see javadoc for Cipher class for more info, e.g.
        Cipher cipher = Cipher.getInstance("AES/GCM/PKCS5Padding");

        GCMParameterSpec gps = new GCMParameterSpec(128, ivBytes);

        cipher.init(Cipher.ENCRYPT_MODE, key, gps);
        byte[] encrypted = new byte[cipher.getOutputSize(message.length)];
        int enc_len = cipher.update(message, 0, message.length, encrypted, 0);
        enc_len += cipher.doFinal(encrypted, enc_len);
        return encrypted;
    }
public static byte[] decrypt(byte[] cipher_text) 
            throws Exception
    {
        // wrap key data in Key/IV specs to pass to cipher
        SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");
        // create the cipher with the algorithm you choose
        // see javadoc for Cipher class for more info, e.g.
        Cipher cipher = Cipher.getInstance("AES/GCM/PKCS5Padding");

        GCMParameterSpec gps = new GCMParameterSpec(128, ivBytes);

        cipher.init(Cipher.DECRYPT_MODE, key, gps);
        byte[] decrypted = new byte[cipher.getOutputSize(cipher_text.length)];
        int dec_len = cipher.update(cipher_text, 0, cipher_text.length, decrypted, 0);
        dec_len += cipher.doFinal(decrypted, dec_len);
        return decrypted;
    }
public static void main(String[] args) {
        String pass = "hello";
        try {
            deriveKeyAndIV(pass);
            byte[] tmp = encrypt("world!".getBytes());
            System.out.println(new String(Base64.getEncoder().encode(tmp)));
            System.out.println(new String(tmp));
            System.out.println("encrypted:\t" + bytesToHex(tmp));
            System.out.println("key:\t" + bytesToHex(keyBytes));
            System.out.println("iv:\t" + bytesToHex(ivBytes));
            tmp = decrypt(tmp);

            System.out.println("decrypted:\t" + bytesToHex(tmp));
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

Sample output:

5xwfm037nXfGS06V5OKgW/oo6WDuow==
��M��w�KN���[�(�`�
encrypted:  E71C1F9B4DFB9D77C64B4E95E4E2A05BFA28E960EEA3
key:    6D525D38BFF7F70AD25205E97368C197
iv: 060374643557ED8E2F6A215F1B6DBD0E
decrypted:  776F726C6421

I copied the Base64 output into a file (test-in), and tried decrypting it using the following command:

openssl enc -d -base64 -id-aes128-GCM -K 6D525D38BFF7F70AD25205E97368C197  -in ~/Desktop/test-in -out ~/Desktop/test-out -iv 060374643557ED8E2F6A215F1B6DBD0E

I got a bad decrypt error message (exit code: 1). trying different modes (id-aes192-GCM and id-aes256-GCM) resulted the same.

What I'm doing wrong?

Here is the OpenSSL wiki page on EVP Authenticated Encryption and Decryption. OpenSSL will decrypt the Java data, but you have to write a C program to do it. You can't use the command line tools. — jww
– jww, Commented Dec 21, 2014 at 21:15

jww · Accepted Answer · 2014-12-21 21:06:48Z

1

I copied the Base64 output into a file (test-in), and tried decrypting it using the following command ...

Authenticated encryption modes do not work from the command line tools. From the openssl enc man page:

The enc program does not support authenticated encryption modes like CCM and GCM. The utility does not store or retrieve the authentication tag.

I know the documentation was recently updated (circa May or June 2014) with the statement above. The mailing list message that triggered it was v1.0.1g command line gcm error.

I don't know if newer versions of the tools (like openssl enc in 1.0.2 or 1.1.0) provide a meaningful error message, or if you just get bad decrypt.

What I'm doing wrong?

Nothing.

answered Dec 21, 2014 at 21:06

jww

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Comments

Hans Z. · Accepted Answer · 2014-12-19 14:04:20Z

1

it may be a bug, see: http://openssl.6102.n7.nabble.com/1-1-0-dev-AES-GCM-on-command-line-quot-bad-decrypt-quot-but-seems-to-work-td49979.html, even this does not entirely work:

KEY=6D525D38BFF7F70AD25205E97368C197
IV=060374643557ED8E2F6A215F1B6DBD0E
echo "world!" | openssl enc -id-aes128-GCM -K $KEY -iv $IV | openssl enc -d -id-aes128-GCM -K $KEY -iv $IV
world!
bad decrypt

answered Dec 19, 2014 at 14:04

Hans Z.

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