Abstract: A method for operating a first computational device to facilitate the secure transfer of a message between the first computation device and a second computational device is described. The method comprises operating the first computational device according to the following steps: forming an encrypted message from the message on the basis of a key derived from one or more codes associated with the second computational device; transmitting the encrypted message to the second computational device; purging the message and the encrypted message from the first computational device; receiving the encrypted message and said one or more codes from the second computational device; upon decrypting the message on the basis of the one or more codes transmitting the decrypted message to the second computational device.