Differences Between this Book and Computer Security: Art and Science
The differences between this book and Computer Security: Art and Science result from the different intended audiences. This book is a shorter version of the latter, omitting much of the mathematical formalism. It is suited for computer security professionals, students, and prospective readers who have a less formal mathematical background, or who are not interested in the mathematical formalisms and would only be distracted by them, or for courses with a more practical than theoretical focus.
The foundations and policy sections of this book do not present results involving formal modeling or derivations of limits on the decidability of security (although it does present the central result, that the generic safety problem is undecidable). Some policies, significant in the history of the development of policy models but no longer used widely, have been omitted, as has discussion of the notions of nondeducibility and noninterference. Further, the section on assurance omits the presentation of formal methods and the detailed discussion of designing and building secure systems. It preserves the exposition of the basic concepts and ideas, especially those related to reference monitors, and discusses commonly encountered evaluation criteria.
The reasons for these differences come from the different backgrounds expected of readers. This book is intended for readers who may not be familiar with highly mathematical concepts, or for classes in which the instructor does not intend to expound upon formalisms, such as those required for the development of high assurance systems, but wants students to be exposed to the ideas underlying a "high assurance system." These situations most often arise in classes in which students' backgrounds may not include classes that provide the understanding needed to assimilate the mathematical details of the work. As a consequence, students are often intimidated by the formalism even if the instructor skips it. The original version of this book is intended for classes where the instructor wishes to explain, or allow the students to explore on their own, the rich mathematical background and formalisms of computer security.
Some students learn best by an informal description of a subject. What is the intuition underlying the ideas and principles of the field? How does the practitioner apply these to improve the state of the art? For these students, this version of the book is more appropriate. Other students are most comfortable with intuition augmented by a formal mathematical exposition of the underlying concepts. How does one make the intuition formal? How does one apply the ideas rigorously to assure a secure system (for an appropriate definition of security)? For these students, the original book, Computer Security: Art and Science, would be more appropriate.
Practitioners who are less interested in mathematical expositions of the theories underlying computer security will find this version more to their liking. This version keeps the intuitive, non-mathematical exposition of the underlying principles, but does so using a small amount of formal mathematics. Practitioners will find this version shorter and, most likely, easier to read because they will not be distracted by material they would find irrelevant.
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