Book excerpt: Biometric user authentication techniques evoke an enormous interest by science, industry and society. Scientists and developers constantly pursue technology for automated determination or confirmation of the identity of subjects based on measurements of physiological or behavioral traits of humans. Biometric User Authentication for IT Security: From Fundamentals to Handwriting conveys general principals of passive (physiological traits such as fingerprint, iris, face) and active (learned and trained behavior such as voice, handwriting and gait) biometric recognition techniques to the reader. Unlike other publications in this area that concentrate on passive schemes, this professional book reflects a more comprehensive analysis of one particular active biometric technique: handwriting. Aspects that are thoroughly discussed include sensor characteristic dependency, attack scenarios, and the generation of cryptographic keys from handwriting.