/**
     * 
     * @param key
     * @return RC4 cipher
     */
    public static Cipher getArcfour ( byte[] key ) {
        try {
            Cipher c = Cipher.getInstance("RC4");
            c.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(key, "RC4"));
            return c;
        }
        catch (
            NoSuchAlgorithmException |
            NoSuchPaddingException |
            InvalidKeyException e ) {