The paper presents results of an initial investigation of multilevel security for knowledge-based systems. Knowledge-based systems are computer programs that give advice using techniques developed in artificial intelligence research. Although many apparently multilevel knowledge-based systems are now being developed, security requirements have not yet been articulated for them. We adopt the production system model as a generalization of knowledge-based systems. We apply noninterference concepts of multilevel security to the production model, and from this we suggest an approach for achieving multilevel secure production systems. Our approach puts control structures at system low, assigns a single classification to entries in the knowledge base, and provide different views both of the database and of the rule base depending upon the clearance of the user. We conclude that it will be possible to achieve multilevel security for many knowledge-based systems. We present a research agenda for further study,

Passwords have long been used as the most common method for providing user authentication when accessing remote computer systems. However, there are many security problems associated with passwords including their susceptibility to the attacks of eavesdropping, playback, and exhaustive search. This paper describes a system which offers an innovative solution to the problem of establishing identities over insecure communications channels. The system embodies the security concept of a one-time pad because it requires that a different password be used for each access. Through the possession of a personal authentication device (the PassPort) and knowledge of a unique PIN number, an authorized user is able to generate the correct password to be used for each access.

The distribution of cryptographic keys in a computer network is discussed.The need for current authentication of communicants to prevent playback attacks is demonstrated, and an earlier protocol is found to be subject to such attacks.A protocol which employs a simple means of obtaining current authentication of communicants and does not require communicants to maintain an absolute sense of time is presented.The protocol is expanded to accommodate key distribution between multiple security communities, where each community is administered by a different authentication server.Another form of the protocol which is appropriate for datagram applications is developed.