Fingerprint Based Biometric Systems

-C Taneja, Sumit Goswami

In the present scenario of increased threat to life, property and information, biometrics is one of the most talked about technology worldwide. In India, the buzz has got mometum with the advent of the UID project. In this article, we demystify the fingerprint based biometrics systems, the techology which utilizes the power of your touch to secure identity and valuable information.

Biometrics: An Introduction

Biometrics refers to the science of identifying or verifying individuals on the basis of some physiological or behavioral characteristics. The idea is to identify a person on the basis of 'who they are' rather than on the basis of 'what they possess' (say ID card) or 'what they remember' (passwords). The characteristics may be physiological --face, fingerprint,

hand, eyes or behavioral traits like voice, signature, and keystroke. Among the different categories of biometric devices, fingerprint is the most common of them. One of the major reasons biometric technologies are gaining prominence today is the fact that unlike passwords, keys and cards, they can't be lost, stolen or relayed. The fingerprinting technology uses the unique ridges and the valleys in the fingerprint as the identifying feature.

Any generic biometric system has certain steps involved in it. First is the enrolment process in which individuals are registered in the biometric system database. The biometric characteristic of the individual is codified to produce a template. The next step is either verification or identification. While the former just verifies if the biometric possessed by the user matches with a profile claimed by him, the latter determines a person's identity using his biometric features.

Let's have a look at the components of a fingerprint based biometric system.

Hardware: that consists of a sensor for the fingerprint to be scanned. The accuracy of the system depends to a large extent on the quality of the scanner used as it directly impacts the quality of the fingerprint.

Software: to transform the scanned information into digital format. Most of them also contain certain enhancement algorithms in order to enhance its quality, image/ template storage, image compression, access logs, etc. Some of the commercial fingerprint softwares available in the market are Verifinger SDK from Neurotechnology, eSSL Timetrack v3, etc.

Database: which acts a repository of the biometric information, ie, fingerprint templates authorized in digital format.

Why Fingerprints?

The cost of a fingerprint based biometric system is quite low in comparison to others like iris and face readers. Fingerprint based systems are quite strong and can be deployed across any kind of environment. This system is less intrusive than iris or retina scans. Most people find it unacceptable to have their pictures taken by video cameras or to speak into a microphone. Finger based systems are more user friendly. Besides, the ability to enroll multiple fingers makes this a very flexible option. It is a proven technology and has been in use for a long time as compared to other nascent technologies.

Case Study

Fingerprint based biometric system is implemented in one of our centres to replacing the earlier manual system. The project was carried out in 4 stages.

In the installation phase, four fingerprint devices each comprising of an optical fingerprint scanner, a monochrome backlit four-line LCD, and a numeric keypad with five menu-control buttons were installed. The devices were connected to the server running the software via Ethernet. Next came the registration stage, in which the enrollment of fingerprints of all employees with details like division names, shifts, date of joining, etc was carried out. Once operational tracking phase began, where employees were supposed to mark their attendance by scanning their fingerprint both in the morning and evening. The system was operated in the testing phase for one month with the manual system being used in parallel and ultimately the manual system was phased out.

The deployment of the system helped drastically reduce the manhours required, paperwork invloved and automated the process almost completely. Some of the problems frequently faced during the implementation process were failure to enroll some users due to less minutiae, rejection of users due improper placement of the finger and medical reasons like arthritis, etc.

Some of the steps taken to counteract the above problems were:

1) A re-enrolment drive was conducted and fresh fingerprints in proper orientation were taken for users facing problems.

2) Multiple fingers were enrolled as backups for several users so that in an event of one finger being rejected, another might be used.

3) Weekly backup of the database storing all the records was taken as a preventive measure so that in case of a crash, valuable data is not lost and system is restored within minutes.

Biometric implementation in

Indian Scenario

We now analyze some of the reasons for the success of biometric sytems in the Indian context. The users of the system are generally well educated white collared employees and well versed with using the system.

To make the system fool proof, the organisation implementing the system would implement a high end biometric system as they have to buy only a few detectors. At many places like in IT industries, the implementers of the system are the users of the system and thus well versed with the equipment. The user group of biometric is very small in places like a shop or a small office and thus false rejects and false acceptance would be very less and not reported in the research studies. In many organizations, the biometric and manual system of attendance are run parallel and thus the rejection rate of biometric is not a botheration as a parallel manual system is in place. Organizations implement biometric access control, but with time, maintaining the same becomes difficult especially in scenarios where there are frequent visitors to the office and with time the usage and the system collapses without reporting the actual FRR or FAR.

Challenges and limitations

There are some general issues that any organisation implementing such a system may face, some of which are outlined below:

Hardware errors : The scanner may reject the fingerprint of the subject at the time of enrollment or at the time of data capture. This maybe due to poor quality of the sensors or reduced sensitivity due to aging, etc.

Software errors : Bugs in the software, improper setting of threshold in the software may also give rise to errors.

Wrong Practice : Since most of the common systems are orientation dependent, improper orientation of the finger on the scanner often causes the system to reject the user.

Biological/Physical reasons : Cuts and bruises on the finger, high/low BP, arthritis and similar diseases also hamper with the working of the system and result in the user being rejected. Some individuals do not have sufficient patterns (ridges and valleys) on their fingers, making it difficult to enroll them.

Medical reasons: There are certain diseases that cause people to lose their fingerprints. Chemotherapy also causes swelling of fingers and loss of fingerprints. Such cases come up as errors in the system.

To minimize such errors, it is advisable to use high quality sensors, a robust algorithm with suitable threshold. Multiple finger prints may be taken to form the templates.

Challenges in the Indian scenario

During our implemenation study, some common features were detected in the Indian scenario which leads to a high rejection rate in the biometric system. Some of them are listed below:

Ladies/Housewives: The ladies involved in cooking get frequent cuts in their fingers during cutting vegetables which changes the fingerprint beyond acceptance range

Tobacco Chewers: A huge population uses chewing tobacco (khaini) which has to be grinded well on the palm with fingers. The grinding of tobacco is done with lime (chuna). With time, the process eliminates all the fingerprints of the user. Such users can't be even enrolled to the biometric system.

Change in Skin: It has been seen in many people that their skin changes with time. The upper thin layer of the skin comes out on a regular time period during which the system rejects them due to change in pattern. With time as the new skin gets harder, they may get accepted by the system again. Incase there is a relatively high percentage of change in the patterns with the new skin, the rejection persists.

Farmers and Factory Workers: With the passage of time, the farmers and the factory workers lose their finger print pattern due to constant tight holding of the farm and industry equipment and friction of it.

Shrinkage in extreme cold: The rejection rate increases in winters as the skin gets shrink in extreme cold in the northern regions of India.

Ladies applying Mehendi: The ladies apply Mehendi during various traditional functions or otherwise and this leads to the rejection of their fingerprint.

Other Physiological Parameters: It has been observed that a few people don't possess fingerprint at all, the fingers are too thin to be detected between sensors etc.

As we have seen, the challenges may be innumerable but the techonology holds great potential especially when used in multimode i.e. where fingerprint may be used with another biometric like iris to further enhance the security features. The use may not be limited to just security but will extend to verification, access control, ID management for civil as well as criminal applications, in banks, ATMs, airports, educational institutions and so on.

The technology is still in it's nascent phase in terms of deployment in the Indian scenario. The coming years will see the biometric storm causing a stir across all sectors from the financial sector to heathcare. Lets hope to soon to enter into a secure world sans any passwords, cards and tokens.