If you have seen movies where the bad guys— or sometimes even the good guys! —must break into a secure facility by impersonating another person’s fingerprints or voice, then you are already familiar with biometric locks.

Biometric fingerprint door locks are ways of using unique physiological characteristics to determine who has access to a certain place.

While the systems in movies seem nearly foolproof which forcing characters to resort to creative and sometimes gruesome methods to trick them, real systems are not infallible.

False Positives

When working properly, biometric devices are much more reliable than password based security such as keypads with personal identification numbers. However, there is always the possibility that a biometric system will incorrectly match the input (voice, facial structure, fingerprint, etc) with that which is stored in the database.

The probably that this will happen is known as false accept rate (FAR) or false match rate (FMR).

These ratios are calculated by dividing the number of false acceptances by the total number of attempts.

For example, a system which has registers 10 total attempts, 5 of which were false matches, has a FAR/FMR of 50% (5 / 10 = .5).

No one wants a system which can be easily compromised. For this reason, you might be curious what the cause of a false acceptance or match is.

These false positives can usually be attributed to faulty hardware or software such as cheap sensors in the machine or poorly written code.

A false match is not necessarily alarming.

In fact, while a false match might be highly improbable, it is always possible. Of course, if you control access to something with a biometric device, you want the FAR or FMR to be a close to zero as possible.

A false match rate of 1% is usually considered acceptable.

What This Means To You

If you are new to the market of biometric locks, make sure to do your research first. It can be helpful to find first-hand experience (reviews) from people who have already used the equipment you are considering. This can give you a realistic idea of how reliable biometric devices are.

In addition to this, look for false accept rates in product descriptions. The rate will be described as "< 1/100000" which means that less than one out of one hundred thousand attempts will result in a false match (a FAR/FMR of .0001%).

Before buying the most expensive biometric device, be sure to consider its use, however.

A fingerprint scanner on a safe, for home use, may not need a false match rate as low as a biometric door lock in a research and development plant.

If you are considering replacing your current biometric locks, you should first determine whether or not your current system can be adjusted.

If you can increase the sensitive to reduce the rates of false acceptances, you might be able to save yourself time and money.

However, the more sensitive your system is, the greater likelihood of it giving false rejection.