Foolproof fingerprint detection

Access & Identity Management Handbook 2013 Access Control & Identity Management

There are two measurable aspects with regard to the success of a biometric solution. Firstly, there is the security aspect in terms of enhancing the system and making it harder to circumvent than other systems such as card readers or PIN-based readers. In addition, it is easier to use and requires less motor operation than other systems – where the card could be easily left at home.

“The reality is that any access or security system is there to buy time for the control room or security manager to send a reaction team to divert a possible criminal act. A biometric system takes longer and is harder to circumvent and affords the security team more time to establish what threat is present and what action to take,” said Jonathan Kahn, MD of Virdi Distribution.

He cites an example. “Safes are rated based on how many hours are required to crack them. Obviously the higher the rating, the longer it will take even an experienced safebreaker to open. Criminals would then be forced to plan their event around the expected numbers of hours as per the safe’s rating.

“Another example is that many people believe that their homes are burglar proof due to the large number of security measures they have in place. However, given the correct tools and skills, most security systems can be circumvented, provided that there is sufficient time to do so.”

Similarly, the majority of commercially available biometric technology readers can also be circumvented. “This is exacerbated by the proliferation of information provided in the public domain on how to outwit security systems, as evidenced on a number of popular TV programmes and by using Google.”

“Programmes like Myth Busters, Nikita and CSI screen information on how to produce and use a fake fingerprint. Stories of students with time on their hands using these methodologies to access supposedly secure locations abound and media noise surrounding bypassing of e-gates at passport control facilities is increasing,” Kahn added.

Choosing the right system

Kahn pointed out that because of the inherent similarity in technology within biometric solutions, there are certain differentiating factors that should be considered when choosing a suitable biometric system.

“Firstly, the size of the sensors should not be a deciding factor. Following that, detection units should be able to identify both live and fake fingerprints. The majority of readers classify fingerprints based on certain patterns in the loops, whorls and arches apparent in the actual fingerprint. Virdi has added a fourth category – that of ‘undetermined’. If you know where the minutia points are and you know you are dealing with a whorl, then you can build a replica of the fingerprint so a sensor can detect it.

The ability to enrol the largest humanly possible number of users means that your system provides you with increased convenience. “It is a commonly known fact that not all readers can enrol all users. For example, an injury to a digit could exclude a user from the system because of predetermined specifications. Another example is those people with dry fingers, which means an absence of detail available. On the other hand, a finger that is too wet will mean that the captured image is too dark for correct determination.”

Intelligent image capture from Virdi measures the degree of dryness on a finger and auto-calibrates the scan. In addition, the algorithm measures and identifies other characteristics of the fingerprint which are unique, in addition to measuring the minutia points to identify the user.

The traditional method is that where lines start, end and intersect, the algorithm should plot these points and measure the relationship between them to build a template. The issue here is that if there are not sufficient points the print will fail to register. However, if you have a pattern-based system, the algorithm is irrelevant. Minutia are not 100% unique. Virdi uses calibration of minutia points and others to enrol the fingerprint.

Dual technology foils criminals

Unlike traditional biometric systems which have fake fingerprint or live fingerprint detection capabilities, Virdi biometric readers come standard with both features. By having both technologies in one reader, criminals will be unable to use false fingerprints to access properties.

Kahn explained that live fingerprints rely on temperature, electrical capacitance and pulse to provide proof of authenticity that the owner of the fingerprint is alive. “However, these can be defeated by holding the false fingerprint until a certain temperature is achieved; by transferring capacitance with a saline solution; and mimicking a pulse by transferring a fingerprint to a transparency and placing another live fingerprint behind this transparency.”

With fake fingerprints there are a number of methods used for identification. One example of circumvention could include blocking off the capacitance. Virdi has a four-tiered approach used to undermine these avoidance techniques. This incorporates IR scanning technology with the ability to identify the material the fingerprint is made of (chemical composition) such as silicon, rubber, paper, plastic, gel, etc; a capacitive sensor built into the optical scanner to measure electrical discharge; intelligent algorithm to measure and compare image distortion; and multi-spectral sensor capabilities.

For more information contact Virdi Distribution, 086 118 4734,,


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