Authentication insures that a user is who they say they are. Authorization limits a user's access to data and protocols. Integrity assures that information has not been modified by unauthorized parties. Privacy assures that information cannot be read by unauthorized parties, particularly when using shared media.
Firewalls allow authorized users access to a network or computer system.
Dial back modem access insures the source of a connection request. Integrity Check Values are checksums computed via keyed algorithms. Key management is part of a complete security system, but is usually separate, or partly separate, from other algorithms. Encryption is a two-way keyed function that scrambles data before transmission and unscrambles it upon reception. Interception of this data does not necessarily mean it can be read.