Biometric identification systems can grouped based on the main physical feature that lends itself to biometric identification:
Fingerprint ridges are formed in the womb; you have fingerprints by the fourth month of fetal development. Once formed, fingerprinted ridges are like a picture on the surface of a balloon. As the person ages, the fingers get larger. However, the relationships between the ridges stayed the same, just like picture on a balloon is still recognizable as the balloon is inflated.
Hand geometry is the measurement and comparison of the different physical characteristics of the hand. Although the hand geometry does not have the same degree of permanence or individuality as some other characteristics, it is still a popular mean of biometric authentication.
Palm Vein Authentication
This system uses an infrared beam to penetrate the users hand as it is waved over the system; the veins within the palm of the user are returned as black lines. Palm vein authentification has a high level of authentication accuracy due to the complexity of vein pattern of the palm. Because the palm vein pattern are internal to the body, this would be difficult system to counterfeit. Also, the system is contactless and therefore hygienic for use in public areas.
A retina scan provides an analysis of the capillary blood vessels located in the back of the eye; the pattern remains the same throughout life. A scan uses low-intensity light to take an image of the pattern formed by the blood vessels. Retina scans were first being suggested in the 1930's.
An iris scan provides an analysis of the rings, furrows and freckles in colored ring that surrounds the pupil of the eye. More than 200 point are used for comparison. Iris scans were proposed in 1936, but it was not the until early 1990's that algorithms for iris recognition were created (and patented). All current iris recognition systems uses these basic patents, held by the Iridian Technologies.
Facial characteristics (the size and shape of facial characteristics, and their relationships to each other). Although this is method that human beings have always used with each other, it is not easy to automate itself. Typically, this method uses the relative distances between common landmarks on the face to generate a unique "faceprint."
Although the way you sign ur name does change over time, and can be consciously changed to some extent, it provides a basic means of identification.
The analysis of pitch, tone, cadence and frequency of a person's voice.