RSA encryption in Java

Question

I am trying to write an encryption algorithm using RSA in Java, I am getting a "javax.crypto.BadPaddingException: Data must start with zero"; I do not know what is this exception for. This is the example I used here

and Here is my code; please help.

public byte[] getEncryptedValue(byte[] bytes, PublicKey key) {
    try {
        cipher.init(Cipher.ENCRYPT_MODE, key);
        return blockCipher(bytes, Cipher.ENCRYPT_MODE);
    } catch (Exception ex) {
        Logger.getLogger(SecurityUtil.class.getName()).log(Level.SEVERE, null, ex);
    }
    return null;
}

public byte[] getDecryptedValue(byte[] bytes, PrivateKey key) {
    try {
        cipher.init(Cipher.DECRYPT_MODE, key);
        return blockCipher(bytes, Cipher.DECRYPT_MODE);
    } catch (Exception ex) {
        Logger.getLogger(SecurityUtil.class.getName()).log(Level.SEVERE, null, ex);
    }
    return null;
}

private byte[] append(byte[] prefix, byte[] suffix) {
    byte[] toReturn = new byte[prefix.length + suffix.length];
    System.arraycopy(prefix, 0, toReturn, 0, prefix.length);
    System.arraycopy(suffix, 0, toReturn, prefix.length, suffix.length);
    return toReturn;
}

private byte[] blockCipher(byte[] bytes, int mode) throws IllegalBlockSizeException, BadPaddingException {
    byte[] scrambled = new byte[0];
    byte[] toReturn = new byte[0];blocks (because of RSA)
    int length = (mode == Cipher.ENCRYPT_MODE) ? 100 : 128;
    int n = 0;
    byte[] buffer = new byte[length];

    for (int i = 0; i < bytes.length; i++) {
        if ((i > 0) && (i % length == 0)) {
            n = 0;
            scrambled = cipher.doFinal(buffer);
            toReturn = append(toReturn, scrambled);
        }
        buffer[i % length] = bytes[i];
        n++;
    }
    ***scrambled = cipher.doFinal(buffer, 0, n);*** <-- the exception is caught here
    toReturn = append(toReturn, scrambled);
    return toReturn;
}

Answer 1

The problem could be the data sent over the network using sockets may be corrupted due to some encoding problems. I had the same problem while developing a simple client/server chat program that encrypts/decrypts using asymmetric key the messages between the server and client and vise versa, instead of sending the message as a string, I sent it as a byte array which is the encrypted message.