Improvements in and relating to autoteller systems.

摘要

An autoteller system 10 comprises an encryption module 30 for encrypting and decrypting data on user cards and for encrypting and decrypting data communicated between it 10 and a remote host 22. The system is characterised by a key loader 58 containing algorithm performance instructions on a ROM 88 removably connectable to the encryption module 30 for the generation of a master key for an encryption circuit 152 to use the master key to encrypt a sub-key for the encrypted sub-key to be used as a session key when encrypting or decrypting data from a user card. The system is further characterised by the keys being stored in a battery-maintained RAM 108 which is volatile if the encryption module 30 is removed. The system is further characterised by the host 22 being operable to provide the autoteller 10 with a plurality of communication keys where any selected named communication key can be used for encrypting and decrypting data communicated between the system 10 and the host 22. The system 10 is yet further characterised by the communications keys supplied to the system 10 being the result of encryption of decryption by the encryption module 30 of sub-keys from the host 22.