A request about the restriction on decrypt and encypt on same object

[Anthony Winner]

I know that generally it's a bad idea, but I've run into an instance where I need to do a duplex use of a crypto object. I have an embedded device, that I need to use that does this very thing, i.e. use the same state for two way communication. 
To use it I've made a bit of a hack, of resetting the _next to allow me to reuse the object for bot decrypt and encrypt, i.e.

At init:

        self.cipher = AES.new(key.encode("utf-8"), AES.MODE_CFB, self.iv.encode("utf-8"))

        # Save the _next state of the cipher, for duplex hack

        self.cipherCp = self.cipher._next

At Tx:

                        self.cipher._next = self.cipherCP

                        temp_buf = self.cipher.encrypt(bytes(tx_buf))

At Rx:

                    self.cipher._next = self.cipherCP

                    pkt.extend(self.cipher.decrypt(self.ser_dev.read(rx_size)))

This works, but I would rather not have to hack into the internals this way. Any way to get a flag or something to allow duplex use of an object? 
BTW, Pycrypt allowed this to work....