C# to Java TripleDES , different results

Question

I'm attempting to convert this C# encryption algorithm to Java; however, I keep retrieving slightly different encrypted results (haven't tried decryption yet). It may also be important to point out that I'm not able to change the C# code.

However when I call the encrypt function in C# on the string "test" it will return nmj8MjjO52y928Syqf0J+g== However in Java it'll return C6xyQjJCqVo=

The C#

private static String key = "012345678901234567890123";

public static string encrypt(String stringToEncrypt)
{
    TripleDES des = CreateDES(key);
    ICryptoTransform ct = des.CreateEncryptor();
    byte[] input = Encoding.Unicode.GetBytes(stringToEncrypt);
    byte[] output = ct.TransformFinalBlock(input, 0, input.Length);
    //return output;
    return Convert.ToBase64String(output);
}


public static String decrypt(string encryptedString)
{
    byte[] input = Convert.FromBase64String(encryptedString);
    TripleDES des = CreateDES(key);
    ICryptoTransform ct = des.CreateDecryptor();
    byte[] output = ct.TransformFinalBlock(input, 0, input.Length);
    return Encoding.Unicode.GetString(output);
}


public static TripleDES CreateDES(string key)
{
    MD5 md5 = new MD5CryptoServiceProvider();
    TripleDES des = new TripleDESCryptoServiceProvider();
    des.Key = md5.ComputeHash(Encoding.Unicode.GetBytes(key));
    des.IV = new byte[des.BlockSize / 8];
    return des;
}

My Attempt with converting to Java

private static String key = "012345678901234567890123";

public static void main(String[] args) throws Exception {
    String text = "test";
    String codedtext = encrypt(text);
    //String decodedtext = decrypt(codedtext);

    System.out.println(new String(codedtext));
    //System.out.println(decodedtext); 
}

public static String encrypt(String message) throws Exception {
    MessageDigest md = MessageDigest.getInstance("md5");
    byte[] digestOfPassword = md.digest(key.getBytes("unicode"));
    byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24);
    //for (int j = 0, k = 16; j < 8;) {
    //  keyBytes[k++] = keyBytes[j++];
    //}

    SecretKey key = new SecretKeySpec(keyBytes, "DESede");
    IvParameterSpec iv = new IvParameterSpec(new byte[8]);
    Cipher cipher = Cipher.getInstance("DESede/CBC/PKCS5Padding");
    cipher.init(Cipher.ENCRYPT_MODE, key, iv);

    byte[] plainTextBytes = message.getBytes();
    byte[] cipherText = cipher.doFinal(plainTextBytes);

    String output = Base64.encode(cipherText);

    return output;
}

public static String decrypt(String message) throws Exception {
    byte[] messageBytes = Base64.decode(message);

    MessageDigest md = MessageDigest.getInstance("md5");
    byte[] digestOfPassword = md.digest(key.getBytes());
    byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24);
    for (int j = 0, k = 16; j < 8;) {
        keyBytes[k++] = keyBytes[j++];
    }

    SecretKey key = new SecretKeySpec(keyBytes, "DESede");
    IvParameterSpec iv = new IvParameterSpec(new byte[8]);
    Cipher decipher = Cipher.getInstance("DESede/CBC/PKCS5Padding");
    decipher.init(Cipher.DECRYPT_MODE, key, iv);

    byte[] plainText = decipher.doFinal(messageBytes);

    return new String(plainText);
}

Does anyone see what I'm overseeing?

Answer 1

You are missing two things. You are using a 16 length key on the c# side since it is not padded like the Java version. By default if the key is 16 bytes in length it will be padded with the first 8 bytes of the key.

To make this match on the Java side you will have to uncomment that line that adds the padding to the key:

for (int j = 0, k = 16; j < 8;) {
  keyBytes[k++] = keyBytes[j++];
}

SecretKey secretKey = new SecretKeySpec(keyBytes, 0, 24, "DESede");

Also, on the java side there was a suggestion to make sure to use UTF-LE for the text. Make sure to use it for everything. So the lines:

byte[] digestOfPassword = md.digest(key.getBytes("UTF-16LE"));

byte[] plainTextBytes = clearText.getBytes("UTF-16LE");

In general I would make sure to set the c# params of all the tripledes object, and not depend on defaults.

Here are two versions that match in c# and java

Java

String key = "012345678901234567890123";
String clearText = "test";

MessageDigest md = MessageDigest.getInstance("md5");
byte[] digestOfPassword = md.digest(key.getBytes("UTF-16LE"));

byte[] keyBytes = Arrays.copyOf(digestOfPassword, 24);
String byteText = Arrays.toString(keyBytes);

for (int j = 0, k = 16; j < 8;) {
  keyBytes[k++] = keyBytes[j++];
}

SecretKey secretKey = new SecretKeySpec(keyBytes, 0, 24, "DESede");

IvParameterSpec iv = new IvParameterSpec(new byte[8]);
Cipher cipher = Cipher.getInstance("DESede/CBC/PKCS5Padding");

cipher.init(Cipher.ENCRYPT_MODE, secretKey, iv);

byte[] plainTextBytes = clearText.getBytes("UTF-16LE");
byte[] cipherText = cipher.doFinal(plainTextBytes);

String output = Base64.encode(cipherText);

c#

string clearText = "test";
string key = "012345678901234567890123";
string encryptedText = "";

MD5 md5 = new MD5CryptoServiceProvider();
TripleDES des = new TripleDESCryptoServiceProvider();
des.KeySize = 128;
des.Mode = CipherMode.CBC;
des.Padding = PaddingMode.PKCS7;

byte[] md5Bytes = md5.ComputeHash(Encoding.Unicode.GetBytes(key));

byte[] ivBytes = new byte[8];


des.Key = md5Bytes;

des.IV = ivBytes;

byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);

ICryptoTransform ct = des.CreateEncryptor();
using (MemoryStream ms = new MemoryStream())
{
    using (CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write))
    {
        cs.Write(clearBytes, 0, clearBytes.Length);
        cs.Close();
    }
    encryptedText = Convert.ToBase64String(ms.ToArray());
}

Edited: Both versions now return the test case result "nmj8MjjO52y928Syqf0J+g=="