Question

I have a DLL in C# that encrypts and decrypts string texts (something basic), but now I need to implement the same encryption method in Java, so that some applications can encrypt data and send it to the library.

I can’t modify the C# code, because it’s already in production, but the Java don’t, so please, any suggestion must be done at the Java side.

Basically I’m trying to implement the same C# encryption method in Java. Here are my C# codes:

NOTE: the passphrase, salt, etc. values obviously are just referential.

    const string PassPhrase = "IhDyHz6bgQyS0Ff1/1s="; 
    const string SaltValue = "0A0Qvv09OXd3GsYHVrA=";   
    const string HashAlgorithm = "SHA1";                
    const int PasswordIterations = 3;                 
    const string InitVector = "GjrlRZ6INgNckBqv";      
    const int KeySize = 256;


public static string Encrypt(string plainText)
    {

        byte[] initVectorBytes = Encoding.ASCII.GetBytes(InitVector);
        byte[] saltValueBytes = Encoding.ASCII.GetBytes(SaltValue);


        byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);


        PasswordDeriveBytes password = new PasswordDeriveBytes(
                                                        PassPhrase,
                                                        saltValueBytes,
                                                        HashAlgorithm,
                                                        PasswordIterations);


        byte[] keyBytes = password.GetBytes(KeySize / 8);


        RijndaelManaged symmetricKey = new RijndaelManaged();


        symmetricKey.Mode = CipherMode.CBC;


        ICryptoTransform encryptor = symmetricKey.CreateEncryptor(
                                                         keyBytes,
                                                         initVectorBytes);


        MemoryStream memoryStream = new MemoryStream();


        CryptoStream cryptoStream = new CryptoStream(memoryStream,
                                                     encryptor,
                                                     CryptoStreamMode.Write);

        cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);


        cryptoStream.FlushFinalBlock();


        byte[] cipherTextBytes = memoryStream.ToArray();


        memoryStream.Close();
        cryptoStream.Close();


        string cipherText = Convert.ToBase64String(cipherTextBytes);


        return cipherText;
    }


public static string Decrypt(string cipherText)
    {

        byte[] initVectorBytes = Encoding.ASCII.GetBytes(InitVector);
        byte[] saltValueBytes = Encoding.ASCII.GetBytes(SaltValue);


        byte[] cipherTextBytes = Convert.FromBase64String(cipherText);

        PasswordDeriveBytes password = new PasswordDeriveBytes(
                                                        PassPhrase,
                                                        saltValueBytes,
                                                        HashAlgorithm,
                                                        PasswordIterations);


        byte[] keyBytes = password.GetBytes(KeySize / 8);


        RijndaelManaged symmetricKey = new RijndaelManaged();


        symmetricKey.Mode = CipherMode.CBC;


        ICryptoTransform decryptor = symmetricKey.CreateDecryptor(
                                                         keyBytes,
                                                         initVectorBytes);


        MemoryStream memoryStream = new MemoryStream(cipherTextBytes);


        CryptoStream cryptoStream = new CryptoStream(memoryStream,
                                                      decryptor,
                                                      CryptoStreamMode.Read);


        byte[] plainTextBytes = new byte[cipherTextBytes.Length];


        int decryptedByteCount = cryptoStream.Read(plainTextBytes,
                                                   0,
                                                   plainTextBytes.Length);


        memoryStream.Close();
        cryptoStream.Close();


        string plainText = Encoding.UTF8.GetString(plainTextBytes,
                                                   0,
                                                   decryptedByteCount);


        return plainText;
    }

Here is my java code, it encrypts the data, but not at the same way as the C# encryption code, so when I try to decrypt it using the C# library it throws the exception: “Length of the data to decrypt is invalid”

    static final String PassPhrase = "IhDyHz6bgQyS0Ff1/1s=";   
    static final String SaltValue = "0A0Qvv09OXd3GsYHVrA=";    
    static final String HashAlgorithm = "SHA1";               
    static final int PasswordIterations = 3;                   
    static final String InitVector = "GjrlRZ6INgNckBqv";       
    static final int KeySize = 256;

public static String encrypt(String plainText)
{
    char[] password = PassPhrase.toCharArray();
    byte[] salt = SaltValue.getBytes();
    byte[] iv = InitVector.getBytes();
    byte[] ciphertext = new byte[0];

    SecretKeyFactory factory;
    try {
        factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA1");

        KeySpec spec = new PBEKeySpec(password, salt, PasswordIterations, 256);
        SecretKey tmp;

        tmp = factory.generateSecret(spec);

        SecretKey secret = new SecretKeySpec(tmp.getEncoded(), "AES");

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secret);
        AlgorithmParameters params = cipher.getParameters();
        //iv = params.getParameterSpec(IvParameterSpec.class).getIV();
        ciphertext = cipher.doFinal(plainText.getBytes("UTF-8"));

    } catch (NoSuchAlgorithmException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (InvalidKeySpecException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (NoSuchPaddingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (InvalidKeyException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } 
    //catch (InvalidParameterSpecException e) {
    //  // TODO Auto-generated catch block
    //  e.printStackTrace();
    //} 
    catch (IllegalBlockSizeException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (BadPaddingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    return Base64.encode(new String(ciphertext));
}

EDIT 1: I fixed the final byte array conversion to String in the Java code, as Jon Skeet suggested.

Answer 1

This is what’s wrong, in the Java code:

return Base64.encode(ciphertext.toString());

You’re calling toString() on the byte array, which will always give a string such as [B@3e25a5.

EDIT: Ooh, just noticed that you can change the Java side. Hooray.

Basically, you need to use a Base64 API which allows:

return Base64.encode(ciphertext);

I’m always disappointed in Base64 APIs which allow you to “encode” a string, to be honest… base64 fundamentally encodes binary data to text, and decodes text data to binary. Oh well…

Anyway, use this API (the encodeBytes method) if you need one which allows you to pass in a byte array.

I haven’t checked over the actual encryption part in detail, but the C# code at least looks like it’s doing the right thing in terms of encodings. It could do with using statements though 🙂