Triple DES Encrypt C# - Decrypt in Java

Question

I\'m getting a Triple DES decrypted string from the clients server, which has been coded in c# (see below):

using System.IO;
using System;
using System.Secur         


        

Answer 1

If someone find himself/herself in the same problem like I did, here is a java implementation (android) of the same .NET decrypt function:

 public static byte[] byteArrayConcat(byte[] array1, byte[] array2) {
        byte[] result = new byte[array1.length + array2.length];
        System.arraycopy(array1, 0, result, 0, array1.length);
        System.arraycopy(array2, 0, result, array1.length, array2.length);
        return result;
    }


 private byte[] fGPKeyTo3DESKey(byte[] GPKey) {

        byte[] _3DESKey = new byte[24];
        byte[] tmp = new byte[8];

        arraycopy(GPKey, 0, tmp, 0, 8);

        _3DESKey = DaPlugUtils.byteArrayConcat(GPKey, tmp);

        return _3DESKey;
    }

 private static byte[] hexStringtoByteArray(String hex) {
        int len = hex.length();

        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(hex.charAt(i), 16) << 4) + Character.digit(hex.charAt(i + 1), 16));
        }
        return data;
    }

public String desDecryptPin(String pin, String encryptKey) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, InvalidKeySpecException {

        int bytesCount = 0;
        int positionCount = 0;


        byte[] bytEncryptedChunk = new byte[8];

        ArrayList Input = new ArrayList();
        bytesCount = pin.length();

        for (int i = 0; i < bytesCount; i += 2) {
            if (positionCount == 8) {
                positionCount = 0;
                Input.add(bytEncryptedChunk);
                bytEncryptedChunk = new byte[8];
            }
            bytEncryptedChunk[positionCount] = (byte) (Integer.parseInt(pin.substring(i, i + 2), 16));
            positionCount++;
        }

        if (positionCount != 0) {
            Input.add(bytEncryptedChunk);
        }


        byte[] _3DESKey = fGPKeyTo3DESKey(hexStringtoByteArray(encryptKey));

        DESedeKeySpec keySpec = new DESedeKeySpec(_3DESKey);
        SecretKey k = SecretKeyFactory.getInstance("DESede").generateSecret(keySpec);
        Cipher cipher = Cipher.getInstance("DESede/ECB/NoPadding");
        cipher.init(Cipher.DECRYPT_MODE, k);


        String res = "";

        for (byte[] bs : Input) {
            byte[] decryptPin = cipher.doFinal(bs);
            String a = new String(decryptPin, StandardCharsets.US_ASCII);

            res += a;
        }

        return res.trim();
    }