Java equivalent of C# DESCrypto

Question

I have DESCrypto in C# and Java as follows. I get the correct results when using C#. I get problem when using Java. How to resolved this problem?

// This is in the main function which will call the crypto function in the security class (C#).

private void button1_Click(object sender, EventArgs e)
{    
    string plainText = "0123456789";
    Debug.WriteLine("plainText:" + plainText ); 
    // plainText:0123456789

    byte[] encrypted = Security.Encrypt(Encoding.ASCII.GetBytes(plainText));
    Debug.WriteLine("encrypted:" + Security.GetString(encrypted)); 
    // encrypted:4F792B474936462B6A4F62635A6142464D54782F4E413D3D

    byte[] decrypted = Security.Decrypt(encrypted);
    Debug.WriteLine("decrypted:" + Encoding.ASCII.GetString(decrypted)); //                               
    // decrypted:0123456789
}

// This is a security class (C#)

public class Security
{
    private static byte[] IV_64 = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 };
    private static byte[] KEY_64 = new byte[] { 7, 1, 7, 7, 5, 5, 4, 7 };

    public static byte[] GetBytes(string value)
    {
        SoapHexBinary shb = SoapHexBinary.Parse(value);
        return shb.Value;
    }

    public static string GetString(byte[] value) 
    {
        SoapHexBinary shb = new SoapHexBinary(value);
        return shb.ToString();
    }

    public static byte[] Decrypt(byte[] value)
    {
        MemoryStream mstream = new MemoryStream(Convert.FromBase64String(Encoding.ASCII.GetString(value)));
        CryptoStream cstream = new CryptoStream(mstream, new DESCryptoServiceProvider().CreateDecryptor(KEY_64, IV_64), CryptoStreamMode.Read);
        StreamReader reader = new StreamReader(cstream);
        return Encoding.ASCII.GetBytes(reader.ReadToEnd());
   }

    public static byte[] Encrypt(byte[] value)
    {
        MemoryStream mstream = new MemoryStream();
        CryptoStream cstream = new CryptoStream(mstream, new DESCryptoServiceProvider().CreateEncryptor(KEY_64, IV_64), CryptoStreamMode.Write);
        StreamWriter writer = new StreamWriter(cstream);
        writer.Write(Encoding.UTF8.GetString(value));
        writer.Flush();
        cstream.FlushFinalBlock();
        mstream.Flush();
        return Encoding ASCII.GetBytes(Convert.ToBase64String(mstream.GetBuffer(), 0, Convert.ToInt32(mstream.Length)));
    }
}

// This is in the main function which will call the crypto function in the security class (Java).

String plainText = "0123456789";
Log.d("test", String.format("plainText:%s\n", plainText)); 
// plainText:0123456789

byte[] encrypted = Security.Encrypt(plainText.getBytes());
Log.d("test", String.format("encrypted:%s\n", Security.GetString(encrypted)));  
// encrypted:3B2F8623A17E8CE6DC65A045313C7F34

byte[] decrypted = Security.Decrypt(encrypted);
Log.d("test", String.format("decrypted: %s\n", String.valueOf(decrypted)));     
// decrypted:[B@6801b34

//This is a security class (JAVA)

import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class Security {
    private static byte[] IV_64 = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 };
    private static byte[] KEY_64 = new byte[] { 7, 1, 7, 7, 5, 5, 4, 7 };

    private static String KEY_TYPE = "DES";
    private static String ALGORITHM = "DES/CBC/PKCS5Padding";

    public static String GetString(byte[] value) {
        StringBuilder builder = new StringBuilder();
        for (byte i : value) {
            builder.append(String.format("%02X", i & 0xff));
        }
        return builder.toString();
    }

    public static byte[] GetByte(String value) {
        StringBuilder builder = new StringBuilder();
        for (char i : value.toCharArray()) {
            builder.append(String.format("%02X", i & 0xff));
        }
        return String.valueOf(builder).getBytes();
    }

    public static byte[] Encrypt(byte[] value) {
        try {
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(KEY_64, KEY_TYPE), new IvParameterSpec(IV_64));
            return cipher.doFinal(value);
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        } catch (BadPaddingException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static byte[] Decrypt(byte[] value) {
        try {
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(KEY_64, KEY_TYPE), new IvParameterSpec(IV_64));
            return cipher.doFinal(value);
        } catch (InvalidKeyException e) {
            e.printStackTrace();
        } catch (InvalidAlgorithmParameterException e) {
            e.printStackTrace();
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (NoSuchPaddingException e) {
            e.printStackTrace();
        } catch (BadPaddingException e) {
            e.printStackTrace();
        } catch (IllegalBlockSizeException e) {
            e.printStackTrace();
        }
        return null;
    }
}

In java, when plainText = "0123456789", expected output from encryption is 4F792B474936462B6A4F62635A6142464D54782F4E413D3D (like in C#), but I get 3B2F8623A17E8CE6DC65A045313C7F34.

Answer 1

In C#, you're encoding the ciphertext with Base64 inside of the Security class and then you encode it again with Hex outside of it. In Java, you're only doing the Hex encoding. You should stick to one encoding and not combine two.

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Other considerations:

• DES should really not be used nowadays. It's rather easy to brute-force.
• If you use CBC mode, then you need to use a new and unpredictable IV every time (randomly generated). It doesn't have to be secret, so you can prepend it to the ciphertext and slice it off before decryption.
• You really should be thinking about adding authentication to the ciphertext. Otherwise, it may be possible to run a padding oracle attack in your system. Either use an authenticated mode like GCM or EAX, or use an encrypt-then-MAC scheme with a strong MAC like HMAC-SHA256.