Address security concepts for mobile-telephone service

Various levels of protection from unauthorized use of a mobile-telephone service can be provided where the exchange for the service is under stored-program control. The security techniques that provide this protection can be upgraded on a per-subscriber or per-system basis as the incidence of unauthorized use increases. The "ultimate" arrangement provides for the encryption of variable passwords. Proper protection of auxiliary storage devices precludes compromise of the cipher-keys assigned to individual mobile units. The techniques that apply and, in particular, those that provide for better security, are more readily implemented in a system with common channel signaling where signaling speeds are considerably faster than those that are used in present-day practice.