There are wide-ranging implications in information security beyond national defense. Securing our information has implications for virtually all aspects of our lives, including protecting the privacy of our—nancial transactions and medical records, facilitating all operations of government, maintaining the integrity of national borders, securing important facilities, ensuring the safety of our food and commercial products, protecting the safety of our aviation system—even safeguarding the integrity of our very identity against theft. Information security is a vital element in all of these activities, particularly as information collection and distribution become ever more connected through electronic information delivery systems and commerce. This book encompasses results of research investigation and technologies that can be used to secure, protect, verify, and authenticate objects and inf- mation from theft, counterfeiting, and manipulation by unauthorized persons and agencies. The book has drawn on the diverse expertise in optical sciences and engineering, digital image processing, imaging systems, information processing, mathematical algorithms, quantum optics, computer-based infor- tion systems, sensors, detectors, and biometrics to report novel technologies that can be applied to information-security issues. The book is unique because it has diverse contributions from the field of optics, which is a new emerging technology for security, and digital techniques that are very accessible and can be interfaced with optics to produce highly effective security systems.