More than skin deep

Silex biometric scanner goes below fingerprints to improve accuracy

Silex S1

|GCN Lab Reviewer's Choice|

Performance: A

Features: A

Value: B+

Price: $129

Reviewer's comments: The S1 scans fingers beyond the first layer of skin to improve accuracy rates for users with really dry hands. It's a little pricey if you aren't having accuracy problems.

Contact: Silex Technology America, Salt Lake City,(801) 748-1199,

LOOKS STRAIGHTFORWARD. But the Silex S1 scans below the first layer of skin, where dryness often foils biometrics.

When the GCN Lab last looked at biometric systems [,], we found that, for the most part, the various sensors did a good job of reading the unique characteristics of our test subjects. Even the least-accurate fingerprint scanner in the review would only miss about five of every 100 tries. Little did we know that where we work has a lot to do with those results.

In a recent meeting with Silex Technology, executives told us about unraveling a mystery: Users in certain areas of the country were reporting bad reads with some of Silex's normally reliable fingerprint scanners.

While users in Washington, D.C., (where GCN is headquartered) and California had little trouble, users in locations such as Colorado and Minnesota were having difficulty logging into systems protected with a biometric scanner. The fact that complaints were clustered in certain geographic areas was puzzling, so Silex officials began trying to figure out what was happening.

After extensive investigation, they found the culprit: dry finger. Dry finger is apparently a condition that commonly occurs in areas of low temperature or low humidity. And in places with both, it's even worse.

Basically, even the latest and greatest biometric sensors tend to have trouble authenticating people who have really dry fingers. (Washington, we can attest, is humid.)

To combat the problem, Silex developed the S1, which is designed to function regardless of atmospheric conditions or a user's water consumption (apparently drinking too little will also affect the accuracy of a standard sensor). We tested an S1 in the lab with a variety of users. We also took extra care to control the lab's atmosphere, with an average temperature of 65 degrees and low relative humidity.

The secret to the S1 sensor is that it's a compact, radio-frequency swipe sensor. It actually scans through the first layer of skin to look at what's beneath. The lower skin layer is called the corium, and it's normally unaffected by surface dryness or dirt and grime. So even if you have a layer of dead, dry skin, you should be able to use this sensor. It is highly detailed and works at a 508-dpi resolution.

Using the S1 sensor is different from using a standard reader and could take some getting used to. There is a series of blue arrows on top of the S1, and you simply run your finger down them like an airplane landing on the deck of a carrier. It took a few tries, because we're used to simply jamming a finger onto a panel. During our tests, novice users actually had a better time of it.

After an extensive search, we found two users with really dry hands. One guy delivers packages for a living, and his hands were exceptionally chapped and scratched. Using a standard biometric sensor (UareU Pro from DigitalPersona) we were able to achieve an 82 percent accuracy rate in scanning his fingers. The other dry subject earned an 88 percent rate. That means roughly one or two in every 10 access attempts resulted in a false negative and an unauthorized user.

Enrolling both subjects through the SX-Biometrics suite and the S1 sensor was not a problem. The S1 connects via a USB 2.0 port to any system running Windows XP or 2000. The software can be used to control access to a system or even restrict access to certain files.

Once enrolled, the S1 did not seem to mind the test subjects' dry, flaky hands. The delivery guy's accuracy jumped to 96 percent and our second subject hit 98 percent.

Average users'with average skin conditions'probably won't see much improvement using the S1. In the lab's cold and dry environment, reviewers achieved 98 to 100 percent accuracy from both scanners. But in government deployments, where agencies are using biometrics for a wide range of people, it makes sense to use one that's reliable across the largest swath of test subjects. The Silex S1 proved to us it's up to the challenge.

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