Noisy data appear very naturally in applications where the authentication is based on physical identifiers. This book provides a self-contained and state-of-the-art overview of the techniques and applications of security based on noisy data. It covers both the theory of authentication based on noisy data and shows it in practice as a key tool for prevention of counterfeiting. Biometrics and physical unclonable functions are discussed extensively. Key new technologies are also discussed. This book can serve as a starting point for PhD students entering the field and will also benefit professionals.