biometric
Any specific and uniquely identifiable physical human characteristic, e.g., of the retina, iris, acoustic spectrum of the voice (i.e., voiceprint), fingerprint(s), handwriting, pattern of finger lengths, etc. , that may be used to validate the identity of an individual.
Note: Biometrics provide a highly secure means of identification, for purposes of security involving, e.g., Internet communications and cryptosystems.