Encryption between Android and C #

Question

I use the following C # source code to encrypt plain text using AES (ECB 256):

public static string Encode(string PlainText) { byte[] Key = ASCIIEncoding.UTF8.GetBytes("12345678901234567890123456789012"); string encrypted = null; RijndaelManaged rj = new RijndaelManaged(); rj.BlockSize = 256; rj.KeySize = 256; rj.Key = Key; rj.GenerateIV(); byte[] IV = rj.IV; rj.Mode = CipherMode.ECB; rj.Padding = PaddingMode.Zeros; try { using (MemoryStream ms = new MemoryStream()) { using (CryptoStream cs = new CryptoStream(ms, rj.CreateEncryptor(Key, IV), CryptoStreamMode.Write)) { using (StreamWriter sw = new StreamWriter(cs)) { sw.Write(PlainText); sw.Close(); sw.Dispose(); } cs.Close(); cs.Dispose(); } byte[] encryptArray = ms.ToArray(); encrypted = (Convert.ToBase64String(encryptArray)); ms.Close(); ms.Dispose(); } } catch (Exception ex) { throw ex; } finally { rj.Clear(); } return encrypted; } 

And I need to decrypt / encrypt data using the same algorithm, but I don't know how to do it.

Here is my Java class ( not working ):

  public static String encrypt(byte[] key, String cleartext, boolean base64) throws Exception { byte[] rawKey = key; byte[] result = encrypt(rawKey, cleartext.getBytes()); // Base 64 if (base64) return toBase64(result); // Hex return toHex(result); } public static String decrypt(byte[] key, String encrypted) throws Exception { byte[] rawKey = key; byte[] enc = toByte(encrypted); byte[] result = decrypt(rawKey, enc); return new String(result); } private static byte[] encrypt(byte[] raw, byte[] clear) throws Exception { SecretKeySpec skeySpec = new SecretKeySpec(raw, "AES"); Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding"); cipher.init(Cipher.ENCRYPT_MODE, skeySpec); byte[] encrypted = cipher.doFinal(clear); return encrypted; } 

Java call:

 encrypt("12345678901234567890123456789012".getBytes(), "Example Message", true); 

I do not know how I can choose the block size or PaddingMode.Zeros in Java.

¿Any idea?

Thanks in advance

Answer 1

Yes, the problem is the 128-bit block size limit in AES (see "Strong cryptography with unlimited power").

Finally, I used GNU Crypto and it works !. I imported all the source code and I deleted the code that I am not using.

If someone wants clean source code , they only need to ask me.

Thanks for the help.

Answer 2

You should also consider Bouncy Castle, it is available for both C # and Java.

http://www.bouncycastle.org

Answer 3

Reading this article , it looks like you might need to use a version of Java that allows you to use cryptography with unlimited power so you can use the large size key (AES-192 and AES-256). They intentionally limit key lengths that can be used by default due to import restriction restrictions imposed by some countries. See the section “Strong curve versus unlimited force” for more information.