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David Cooper's Home Page; David Cooper; Postdoctoral Associate; 4112 Upson Hall; Phone: 607-255-9222; Email: dcooper@cs.cornell.edu; Current Research;My current research involves the design and implementation of a security;architecture for;Horus. The goal of this work is to provide a layer to Horus;which will interact with; The Kerberos;Network Authentication Service and other cryptographic tools in order to;provide privacy and authentication services to processes in a group setting.;The original security architecture for Horus was implemented by Mike Reiter;(see;A Security Architecture for Fault-Tolerant Systems). In the original;implementation of;Horus, all process groups supported the virtual synchrony model of;computation. In order to maintain virtual synchrony (in the crash failure;model used in;Horus), it is necessary for all processes within a group to be honest. As;a result, the original security architecture makes the assumption that any;process which is allowed to join a group is trusted by all of the group members.;In the current version of; Horus, it is;possible to maintain process groups whose semantics are weaker than those of;virtual synchrony. In such groups, it may be desirable to permit untrusted;processes to join. An example of this might involve allowing untrusted clients;to join a client/server group. In such a setting, servers would communicate;with untrusted clients, but would only accept a limited set of commands from;the clients (and would be responsible for screening out all other messages).;The new Horus;security architecture will permit arbitrary trust relationships;among the processes within a group. This is accomplished by using a key;management scheme which does not allow one process in a group to impersonate;another group member. Using this scheme, a process group may trivially achieve;the semantics provided by the original security architecture (however with;a slightly higher overhead). However, unlike the original security architecture,;the new architecture enables the implementation of groups (such as;client/server groups) which many have more complicated trust relationships;among group members.; Thesis Research;In my thesis, I proposed a set of solutions to the privacy problems inherent;in mobile networks. In a static network, there are two basic types of;information which users may wish to keep private. The first is the contents;of the messages that they send to other users. This information can be hidden;with the proper use of encryption. Users may also wish to prevent outsiders;from determining with whom they are communicating. A solution to maintaining;the unlinkability of message senders and recipients was first proposed in 1981;by David Chaum;(Communications of the ACM, February 1981). Since then, several;others have made improvements to the original scheme.;In a mobile network, in addition to the types of information in a static;network, there is also location information. Users who carry mobile;communications devices will, in general, desire privacy. However, the;messages that their devices send and receive may reveal private information;about the devices' owners. In my research, I developed, along with my advisor;Ken Birman, a set of protocols to prevent such attacks from both internal;and external adversaries.; Publications;David A. Cooper and Kenneth P. Birman. Preserving privacy in a network of;mobile computers. In Proceedings of the 1995 IEEE Symposium on Security;and Privacy, pages 26-38, May 1995.;David A. Cooper and Kenneth P. Birman. The design and implementation of a;private message service for mobile computers. Wireless Networks, 1995.;David Anthony Cooper.;The Design and Implementation of a Private Message Service for Mobile;Computers. Ph.D. dissertation, Cornell University, August 1995.;