Configuring cryptographic systems

This application aims to provide an improved way of updating the cryptographic systems of aircraft 400. It does so by first generating a cryptographic key configuration (CKC) on a remote terminal that is separate from the aircraft. This is done by first receiving data that is indicative of a user specifying a CKC action 402. It then accesses a database that stores the cryptographic information 404, and generates the CKC 406. The CKC is then transferred to a removable data cartridge, or storage device 408. The user can then engage this device with an avionic transfer system 410, and the avionic transfer system is then automatically configured based on the CKC 412. The cryptographic key configuration can also include data that maps authorised users to cryptographic ignition keys, as well as data that maps one or more cryptographic keys to one or more cryptographic units. The removable data storage device can also include a dedicated key memory that can store cryptographic keys.