Encrypt in C# and Decrypt in Java with same secret key

Question

I am preparing to do encryption in sever side(c#) and decrypt in android side (Java) for my api key. Both encryption/decryption in c# was okay. And also, in java, both encryption/decryption also okay. The main problem is generated ciphertext with C# is different with java although I used the same secret key. C# generated cipher text can't be decrypted in Java. I tried like below.

In Java

 public static String key = "aaaaaaaabbccccbbaaaaaaaabbccccbb";
    private static byte[] key_Array = Base64.decode(key,Base64.DEFAULT);

    public static String encrypt(String plainText)
    {
        try
        {
            Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");

            // Initialization vector.
            // It could be any value or generated using a random number generator.
            byte[] iv = { 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1, 7, 7, 7, 7 };
            IvParameterSpec ivspec = new IvParameterSpec(iv);

            Key secretKey = new SecretKeySpec(key_Array, "AES");
            cipher.init(Cipher.ENCRYPT_MODE, secretKey, ivspec);

            return Base64.encodeToString(cipher.doFinal(plainText.getBytes()),Base64.DEFAULT);
        }
        catch (Exception e)
        {
            System.out.println("[Exception]:"+e.getMessage());
        }
        return null;
    }

    public static String decrypt(String encryptedMessage)
    {
        try
        {
            //Cipher _Cipher = Cipher.getInstance("AES");
            //Cipher _Cipher = Cipher.getInstance("AES/ECB/PKCS5PADDING");
            Cipher _Cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");

            // Initialization vector.
            // It could be any value or generated using a random number generator.
            byte[] iv = { 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1, 7, 7, 7, 7 };
            IvParameterSpec ivspec = new IvParameterSpec(iv);

            Key SecretKey = new SecretKeySpec(key_Array, "AES");
            _Cipher.init(Cipher.DECRYPT_MODE, SecretKey, ivspec);

            byte decodedMessage[] = Base64.decode(encryptedMessage,Base64.DEFAULT);
            return new String(_Cipher.doFinal(decodedMessage));

        }
        catch (Exception e)
        {
            System.out.println("[Exception]:"+e.getMessage());

        }
        return null;
    }

In C#

public class Crypt
    {
        // C# Code, CipherMode.CBC
        // CBC version need Initialization vector IV.

        public static string keyStr = "aaaaaaaabbccccbbaaaaaaaabbccccbb";
                                      // FFClY170hLrhsDnKUEhJ4FhVOnrpNNFFClY170hLrhsDnKUE
        public static string Encrypt(string PlainText)
        {
            RijndaelManaged aes = new RijndaelManaged();
            aes.BlockSize = 128;
            aes.KeySize = 256;

            // It is equal in java 
            /// Cipher _Cipher = Cipher.getInstance("AES/CBC/PKCS5PADDING");    
            aes.Mode = CipherMode.CBC;
            aes.Padding = PaddingMode.PKCS7;

            byte[] keyArr = Convert.FromBase64String(keyStr);
            byte[] KeyArrBytes32Value = new byte[32];
            Array.Copy(keyArr, KeyArrBytes32Value, 24);

            // Initialization vector.   
            // It could be any value or generated using a random number generator.
            byte[] ivArr = { 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1, 7, 7, 7, 7 };
            byte[] IVBytes16Value = new byte[16];
            Array.Copy(ivArr, IVBytes16Value, 16);

            aes.Key = KeyArrBytes32Value;
            aes.IV = IVBytes16Value;

            ICryptoTransform encrypto = aes.CreateEncryptor();

            byte[] plainTextByte = ASCIIEncoding.UTF8.GetBytes(PlainText);
            byte[] CipherText = encrypto.TransformFinalBlock(plainTextByte, 0, plainTextByte.Length);
            return Convert.ToBase64String(CipherText);

        }

        public static string Decrypt(string CipherText)
        {
            RijndaelManaged aes = new RijndaelManaged();
            aes.BlockSize = 128;
            aes.KeySize = 256;

            aes.Mode = CipherMode.CBC;
            aes.Padding = PaddingMode.PKCS7;

            byte[] keyArr = Convert.FromBase64String(keyStr);
            byte[] KeyArrBytes32Value = new byte[32];
            Array.Copy(keyArr, KeyArrBytes32Value, 24);

            // Initialization vector.   
            // It could be any value or generated using a random number generator.
            byte[] ivArr = { 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1, 7, 7, 7, 7 };
            byte[] IVBytes16Value = new byte[16];
            Array.Copy(ivArr, IVBytes16Value, 16);

            aes.Key = KeyArrBytes32Value;
            aes.IV = IVBytes16Value;

            ICryptoTransform decrypto = aes.CreateDecryptor();

            byte[] encryptedBytes = Convert.FromBase64CharArray(CipherText.ToCharArray(), 0, CipherText.Length);
            byte[] decryptedData = decrypto.TransformFinalBlock(encryptedBytes, 0, encryptedBytes.Length);
            return ASCIIEncoding.UTF8.GetString(decryptedData);
        }
    }

Java Output

Plain Text : hla hla

cipher Text: MW6b3AIpNw5RLmhvAro1Yg==

C# Output

Plain Text : hla hla

cipher Text: qsHRHy05GbRv5Q1QNOUlZQ==

Any ideas or alternative ways will be appreciated. Thanks.

Answer 1

The problem is that, in your Java code, you're only using a 192-bit key, while in the C# version, you're using a 256-bit key.

Your base64-encoded key is 32 characters, which translates to 24 bytes, which is only 192 bits.

These are the offending lines in Java:

public static String key = "aaaaaaaabbccccbbaaaaaaaabbccccbb"; // 32 characters
private static byte[] key_Array = Base64.decode(key, Base64.DEFAULT); // 24 bytes

Just changing the creation of your Java key array will fix things. Something like:

public static String key = "aaaaaaaabbccccbbaaaaaaaabbccccbb"; // 32 characters
private static byte[] key_Array = new byte[32]; // 32 bytes

static {
    // copy the 24 base64-decoded bytes to the key array
    System.arraycopy(Base64.decode(key, Base64.DEFAULT), 0, key_Array, 0, 24);
}