Why use biometrics ?

 
There are more people on Earth than ever before, owning more things, and swapping more information every single day. Security has never been more important but—ironically, thanks to the computing power at everyone's disposal—never easier to crack. Traditionally, security relies on things that are difficult to do quickly: locks are physically difficult to bust open without the correct metal keys, while information secured by encryption (computerized scrambling) is hard to access without the right mathematical keys. But this kind of security has a basic flaw: with the right key, even the wrong person can quickly gain access.

Most security experts think biometrics (body measurement) is the answer. Instead of restricting access to things through arbitrary locks and keys, we grant access to people if we can positively identify them by measuring some unique pattern on their body. If you think about it, an ordinary passport photo is a crude example of biometrics. When the border guards look at your face and compare it with your passport photo, what they're doing is intuitively comparing two images. Is one nose bigger than another? Are the eyes further apart? That's simple biometrics. The trouble is that our faces change all the time and lots of people look very similar. Fingerprints are a more reliable form of biometrics, but even they're not infallible: illnesses and injuries, as well as basic wear-and-tear, can alter the pattern of ridges on our fingers in time. Iris scans are a much more reliable way of identifying people - simplying by taking quick photographs of their eyes!

reference:

<www.explainthatstuff.com/how-iris-scans-work.html>