On Distributed System Security

Authorization plays an essential role to ensure the security of a wide variety of computing and IT systems such as data management systems, e-trading systems, database transaction systems, etc. This paper aims to propose a high level formal language for specifying and evaluating distributed authorizations with delegation, develop a new method for credential chain discovery, and implement a system prototype for representing and reasoning about access control policies in distributed environments. By applying the new methodology and technology developed from this work, we will be able to design highly secure computing and IT systems in many different complex problem domains.