Abstract
Authentication protocols are constructed using certain fundamental security mechanisms. This paper discusses how the properties of the underlying mechanisms affect the design of authentication protocols. We firstly illustrate factors affecting the selection of protocols generally. These factors include the properties of the environment for authentication protocols and the resources of the authenticating entities. We then consider a number of authentication protocols which are based on mechanisms satisfying different conditions than those required for the ISO/IEC 9798 protocols, in particular the use of non-random nonces and the provision of identity privacy for the communicating parties.