His research interests include security, privacy, databases, and distributed systems. He has authored or coauthored seven books, edited 53 books and conference proceedings, and published more than 500 technical papers in the refereed journals and conference proceedings. Five of his books have been translated in Chinese. He is also a holder of 25 patents. His current research sponsors are the Army Research Office (ARO), Office of Naval Research (ONR), US Army Combat Capabilities Development Command (DEVCOM), National Security Agency (NSA), National Science Foundation (NSF), Knowledge Based Systems, Inc. (KBSI), and Intelligent Automation, Inc.