Authentication and authorization in distributed systems

The main goal of my research is to propose and study an authentication and authorization framework for distributed systems that is both practical and formal. Specifically, its practicality allows it to serve as a key building block in an overall security infrastructure for distributed systems, while its formality allows the use of rigorous reasoning to ascertain its security properties. To address the basic authentication needs in a distributed system, I have proposed a suite of authentication protocols which, together with the abstractions of credential and certificate, forms a coherent authentication framework. At present, the suite includes a secure bootstrap protocol, a user-host authentication protocol, and a process-process authentication protocol. To formally analyze these protocols, I have developed a new analysis approach based on two basic types of correctness properties--namely, correspondence and secrecy--that I have identified and formalized. My approach consists of several components: a specification language, a semantic model, an assertion language, a notion of satisfaction and procedures for verifying satisfaction. I have successfully applied the approach to verify the protocols in my framework. For authorization, I focus on two underlying problems: representation and protocol design. To address the representation problem, I have identified three types of structural properties commonly encountered in authorization requirements--namely, closure, default and inheritance. These properties can be effectively exploited to reduce the complexity of representing and evaluating authorization in a large-scale distributed system. Based upon these properties, I have designed a practical extension, called generalized access control list (GACL), to the usual access control list. GACL is expressive yet tractable. It serves as a unifying foundation for my framework. For protocol design, I have proposed a suite of protocols for carrying out distributed authorization. Specifically, these protocols allow authorization functions of an end server to be offloaded to dedicated authorization servers.