Biometric Authentication Systems have become inevitable components of modern day security. In this book we have discussed fingerprint, palmprint, finger-knuckle print, face, iris, dynamic signature, keystroke dynamics and their multimodal implementations. In physiological category fingerprints, palmprints & finger-knuckle prints, face & iris are discussed. Their unimodal as well as multimodal implementations are presented. In case of behavioral biometrics dynamic signature & keystroke dynamics for biometric authentication have been investigated. Digital signal & image processing based techniques such as Kekre Wavelets, Kekre's Codebook Generation Algorithms and their variants are used for feature vector generation and recognition purpose. Multimodal systems consisting of the combinations of above mentioned biometric traits are presented. Multi-algorithmic, Multi-instance implementations are presented in this book. A new architecture called as hybrid multimodal system is also presented in this book. This book will be very much helpful for the people who are working in the biometric authentication domain.