US Patent 9467431 Application specific master key selection in evolved networks

An authentication method comprises providing a set of N plural number of master keys both to a user terminal (13) and to home network entity (11) and, when performing an authentication key agreement (AKA) transaction for an application, selecting one of the N number of master keys to serve as a master key for use both at the user terminal and the home network entity for deriving further keys for the application. For example, when performing an authentication key agreement (AKA) transaction for a first application, the method involves randomly selecting one of the N number of master keys to serve as a first master key for use both at the user terminal and the home network entity for deriving further keys for the first application; but when 10 performing an authentication key agreement (AKA) transaction for another application, the method involves randomly selecting another one of the N number of master keys to serve as master key for use both at the user terminal and the home network entity for deriving further keys for the another application.