- Metrics related to human characteristics –
- Physiological – face recognition, iris recognition, finger prints (oldest method), DNA, retina etc.
- Behavioral – gait, voice, typing rhythm
- Iris scan – mathematical analysis of the random pattern in the iris of the eyes by near infra red illumination (not to be confused with retinal recognition i.e. analysis of retinal blood vessels unique to every eye through infra red illumination).
- Fingerprints – the scanner identifies the ridges and valleys of fingers which are saved as encrypted mathematical data not the image of the fingerprint itself.