DATA SECURITY: OPERATING SYSTEMS AND COMPUTER NETWORKS

A great deal of attention has recently been focussed on the reliable protection of data in computer systems and networks. This dissertation examines the class of protection problems known as data security and discusses ways of reliably providing data security.; In the dissertation, the concept of data security is explained and a formal model of its meaning is presented. The UCLA Data Secure Unix Operating System is then described and the model is used to demonstrate, rather intuitively, that the system is indeed secure. The dissertation explains why such clear and intuitive demonstrations of security are a necessary complement to the more complex and formal approaches of others.; The dissertation also examines issues of providing data security in computer networks. Those networks add additional complexity to the data security problem which is solved by the use of encryption. The dissertation explains how encryption can best be integrated into networks, and examines the tradeoffs in using conventional or public-key based encryption algorithms. The emerging issue of digital signatures is also discussed, and several possible implementations are presented. One rather surprising and important conclusion is that for most network security problems, conventional or public-key based encryption systems appear to be equivalent.