scope:

This part of ISO/IEC 9798 specifies entity authentication niechanisim using a cryptographic check function. Two inechanisius are concerned with the authentication of a single entity (unilateral authentication), while the remaining are mechanisuis for mutual authentication of two entities.

The mechanisms specified in this part of ISO/IEC 9798 use time variant paranieters such as time stamps, sequence numbers, or random nunibers, to prevent valid authentication inforination from being accepted at a later time.

If a tinie stamp or sequence nuniber is used, one pass is needed for unilateral authentication, while two passes are needed to achieve mutual authentication. If a challenge and response niethod employing random nunibers is used, two passes are needed for unilateral authentication, while three passes are required to achieve iiiutual authentication.

Examples of cryptographic check functions are given in annex C.