This book is based on the author's advanced undergraduate or beginning graduate course, Computer Security and Reliability, which he has been teaching for the past six years. The author takes an index based quantitative approach to the subject as opposed to the usual verbal or qualitative or subjective case histories. The TWC-Solver, available on an accompanying CD-ROM, contains 10 java-coded, main applications and hundreds of subitems, and assists the reader in understanding the numerical implementations of the book chapters.