Need an Objective-C version of Java Encryption and Base 64 encoding that I already have

Question

I have a Java class that encrypts a string and then converts it to Base64, which is used in an Android Application: (this code was used from this example (note the spaces in the hyperlink): http ://stackoverflow.com/ questions/2090765/encryption-compatable-between-android-and-c)

public class encryption {
public static final String TAG = "smsfwd"
private static Cipher aesCipher;
private static SecretKey secretKey;
private static IvParameterSpec ivParameterSpec;

private static String CIPHER_TRANSFORMATION = "AES/CBC/PKCS5Padding";
private static String CIPHER_ALGORITHM = "AES";
//the secret key in HEX is 'secretkey'
private static byte[] rawSecretKey = {Ox73, Ox65, Ox63, Ox72, Ox65, Ox74, Ox6B, Ox65, Ox79};

private static String MESSAGEDIGEST_ALGORITHM = "MD5";

public encryption(String passphrase) {
    byte[] passwordKey = encodeDigest(passphrase);

    try {
        aesCipher = Cipher.getInstance(CIPHER_TRANSFORMATION);
    } catch (NoSuchAlgorithmException e) {
        Log.e(TAG, "No such algorithm " + CIPHER_ALGORITHM, e);
    } catch (NoSuchPaddingException e) {
        Log.e(TAG, "No such padding PKCS5", e);
    }

    secretKey = new SecretKeySpec(passwordKey, CIPHER_ALGORITHM);
    ivParameterSpec = new IvParameterSpec(rawSecretKey);
}




//base 64 encryption
public String encryptAsBase64(byte[] clearData) {
    byte[] encryptedData = encrypt(clearData);
    return base64.encodeBytes(encryptedData);
}




public byte[] encrypt(byte[] clearData) {
    try {
        aesCipher.init(Cipher.ENCRYPT_MODE, secretKey, ivParameterSpec);
    } catch (InvalidKeyException e) {
        Log.e(TAG, "Invalid key", e);
        return null;
    } catch (InvalidAlgorithmParameterException e) {
        Log.e(TAG, "Invalid algorithm " + CIPHER_ALGORITHM, e);
        return null;
    }

    byte[] encryptedData;
    try {
        encryptedData = aesCipher.doFinal(clearData);
    } catch (IllegalBlockSizeException e) {
        Log.e(TAG, "Illegal block size", e);
        return null;
    } catch (BadPaddingException e) {
        Log.e(TAG, "Bad padding", e);
        return null;
    }
    return encryptedData;
}

private byte[] encodeDigest(String text) {
    MessageDigest digest;
    try {
        digest = MessageDigest.getInstance(MESSAGEDIGEST_ALGORITHM);
        return digest.digest(text.getBytes());
    } catch (NoSuchAlgorithmException e) {
        Log.e(TAG, "No such algorithm " + MESSAGEDIGEST_ALGORITHM, e);
    }

    return null;
}

}

And the base 64 encryption comes from (note the spaces in the hyperlink) http ://iharder.sourceforge.net/current/java/base64/

What happens is that this gets passed to a C#/.net server for decryption and everything works great on the Android. The issue is now converting this to Objective-C for use on the iPhone.

I have done a lot of research and the answer that has come closest is http://dotmac.rationalmind.net/2009/02/aes-interoperability-between-net-and-iphone/

However, when I use that example (code taken straight from the downloaded zip), I'm getting a 'Padding is invalid and cannot be removed.' error server side.

My server side code is:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

using System.Text;
using System.Security.Cryptography;

namespace test.Business
{
    public class Crypto
    {
        private ICryptoTransform rijndaelDecryptor;
        // Replace me with a 16-byte key, share between Java and C#
        private static byte[] rawSecretKey = {Ox73, Ox65, Ox63, Ox72, Ox65, Ox74, Ox6B, Ox65, Ox79};

        public Crypto(string passphrase, bool encrypt)
        {
            byte[] passwordKey = encodeDigest(passphrase);
            RijndaelManaged rijndael = new RijndaelManaged();
            if(encrypt)
                rijndaelDecryptor = rijndael.CreateEncryptor(passwordKey, rawSecretKey);
            else
                rijndaelDecryptor = rijndael.CreateDecryptor(passwordKey, rawSecretKey);
        }

        public Crypto(string passphrase)
        {
            byte[] passwordKey = encodeDigest(passphrase);
            RijndaelManaged rijndael = new RijndaelManaged();
            rijndaelDecryptor = rijndael.CreateDecryptor(passwordKey, rawSecretKey);
        }

        private string Decrypt(byte[] encryptedData)
        {
            byte[] newClearData;

            try
            {
                newClearData = rijndaelDecryptor.TransformFinalBlock(encryptedData, 0, encryptedData.Length);
            }
            catch
            {
                throw;
            }
            return Encoding.ASCII.GetString(newClearData);
        }

        internal string DecyptString(string token)
        {
            //UTF8Encoding utf8 = new UTF8Encoding();
            return Decrypt(ASCIIEncoding.ASCII.GetBytes(token));
        }

        internal string DecryptFromBase64(string encryptedBase64)
        {
            return Decrypt(Convert.FromBase64String(encryptedBase64));
        }

        private byte[] encodeDigest(string text)
        {
            MD5CryptoServiceProvider x = new System.Security.Cryptography.MD5CryptoServiceProvider();
            byte[] data = Encoding.ASCII.GetBytes(text);
            return x.ComputeHash(data);
        }


        //Encryption Code
        public string EncryptAsBase64(string strData)
        {
            byte[] clearData = Encoding.ASCII.GetBytes(strData);
            byte[] encryptedData = Encrypt(clearData);
            return Convert.ToBase64String(encryptedData);
        }

        public byte[] Encrypt(byte[] clearData)
        {
            byte[] test1 = new byte[clearData.Length];
            try
            {               
                test1 = rijndaelDecryptor.TransformFinalBlock(clearData, 0, clearData.Length);               
            }
            catch
            {
                throw;
            }

            return test1;
        }
    }
}

Any ideas? Thank you very very much in advance!

Answer 1

You can get an NSData category to handle Base64 encoding/decoding here:

http://cocoawithlove.com/2009/06/base64-encoding-options-on-mac-and.html

You can find a library and NSData category to do AES encryption here:

http://iphonedevelopment.blogspot.com/2009/02/strong-encryption-for-cocoa-cocoa-touch.html

Between the two, you can replicate what you are doing, and probably with less code...