Biometrics refers to metrics related to human characteristics. Biometric authentication is used as a form of identification and access control. Biometric identifiers are distinctive, measurable characteristics used to label and describe individuals. Biometric identifiers are often categorized as physiological versus behavioral characteristics. Physiological characteristics are related to the shape of a human body. Examples include, fingerprints, palm veins, facial characteristics, iris characteristics, voice characteristics, or the like. Behavioral characteristics are related to patterns of behavior. Examples include typing, rhythm, gait, or the like.