C# to Java Encryption and Decryption

Question

I'm trying to do an Encryption and Decryption in Java Android.

Below is my code for C#, I need to convert it to Java Android. Can someone help me how to do it?

I've been doing this for almost 2 days yet can't find any solutions on how to convert it. I'm newbie in Android.

public static string Encrypt(string toEncrypt)
        {
            byte[] keyArray;
            byte[] toEncryptArray = UTF8Encoding.UTF8.GetBytes(toEncrypt);

            System.Configuration.AppSettingsReader settingsReader = new AppSettingsReader();

            string key = "KEY";

            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
            keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
            hashmd5.Clear();

            TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
            tdes.Key = keyArray;
            tdes.Mode = CipherMode.ECB;
            tdes.Padding = PaddingMode.PKCS7;

            ICryptoTransform cTransform = tdes.CreateEncryptor();
            byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);
            tdes.Clear();
            return Convert.ToBase64String(resultArray, 0, resultArray.Length);
        }

        public static string Decrypt(string cipherString)
        {
            try
            {
                byte[] keyArray;
                byte[] toEncryptArray = Convert.FromBase64String(cipherString);

                string key = "KEY";

                MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();
                keyArray = hashmd5.ComputeHash(UTF8Encoding.UTF8.GetBytes(key));
                hashmd5.Clear();

                TripleDESCryptoServiceProvider tdes = new TripleDESCryptoServiceProvider();
                tdes.Key = keyArray;
                tdes.Mode = CipherMode.ECB;
                tdes.Padding = PaddingMode.PKCS7;

                ICryptoTransform cTransform = tdes.CreateDecryptor();
                byte[] resultArray = cTransform.TransformFinalBlock(toEncryptArray, 0, toEncryptArray.Length);

                tdes.Clear();
                return UTF8Encoding.UTF8.GetString(resultArray);
            }
            catch (Exception)
            {
                return "Invalid";
            }
        }

Answer 1

Try This,

package mypackage;

import java.security.MessageDigest;
import java.util.Arrays;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;

public class Main {

    public static void main(String[] args) throws Exception {

        String text = "neeraj";

        String codedtext = new Main().encrypt(text);

        String decodedtext = new Main().decrypt(codedtext);

        System.out.println(codedtext); // this is a byte array, you'll just see a reference to an array
        System.out.println(decodedtext); // This correctly shows "neeraj"
    }

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

        final SecretKey key = new SecretKeySpec(keyBytes, "DESede");
        final IvParameterSpec iv = new IvParameterSpec(new byte[8]);
        final Cipher cipher = Cipher.getInstance("DES/ECB/PKCS7Padding");
        cipher.init(Cipher.ENCRYPT_MODE, key, iv);

        final byte[] plainTextBytes = message.getBytes("utf-8");
        final byte[] cipherText = cipher.doFinal(plainTextBytes);
        // final String encodedCipherText = new sun.misc.BASE64Encoder()
        // .encode(cipherText);

        return Base64.encodeBase64String(cipherText);
    }

    public String decrypt(String input) throws Exception {

        byte[] message = Base64.decodeBase64(input);

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

        final SecretKey key = new SecretKeySpec(keyBytes, "DESede");
        final IvParameterSpec iv = new IvParameterSpec(new byte[8]);
        final Cipher decipher = Cipher.getInstance("DES/ECB/PKCS7Padding");
        decipher.init(Cipher.DECRYPT_MODE, key, iv);

        // final byte[] encData = new
        // sun.misc.BASE64Decoder().decodeBuffer(message);
        final byte[] plainText = decipher.doFinal(message);

        return new String(plainText, "UTF-8");
    }
}

Refer to the main function for usage.

I have updated my code. Your C# program gives output as a base64 string. But in java the input of decrypt and output of encrypt is byte array. Convert the byte array to base64 and it will work.

For Base64 operation in java you need the Apache Commons codec .

In java 8 you can use java.util.Base64

Answer 2

For the encryption you must go through this coding:

import java.security.MessageDigest;
import java.util.Arrays;
import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.binary.Base64;



public String encrypt(String inputString,String key) throws Exception {

      //----  Use specified 3DES key and IV from other source -------------- 

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

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

     final byte[] plainTextBytes = inputString.getBytes("utf-8");
     final byte[] cipherText = cipher.doFinal(plainTextBytes);
     // final String encodedCipherText = new sun.misc.BASE64Encoder()
     // .encode(cipherText);

     return Base64.encodeBase64String(cipherText);
}