4. Beyond fingerprints

There are more advanced biometric techniques that are used by the military and companies that need very high security; most aren’t practical for everyday use. Scanning the iris or retina requires expensive equipment-retinal scanning is particularly intrusive, because you have to stand still while a light is shined directly into your eye. Voice recognition is unreliable if you have a cold or there’s a lot of background noise, and it would be too easy to use a recording to get past the system.

A whole-hand scanner is far too big and bulky to use at home and it measures the geometry of your hand rather than the print, which may not be different enough between people. Hitachi has a scanner that shines a strong light onto one finger; this matches the pattern of veins under the skin. Not only are vein patterns as unique as fingerprints, they’re invisible until illuminated, so they’d be hard to copy onto a dummy finger. The scanner looks for blood flow as well. On the downside, the hardware is bulky and expensive. Similarly, Fujitsu has a $265 PalmSecure mouse that will scan the veins in your palm.

Scanning the pattern of veins-and looking for blood flow-could be more secure than scanning a fingerprint, but the devices are much bigger and bulkier.

As Webcams become more common, facial biometrics may become an alternative. This technique calculates the characteristics of a face-the distance between the eyes, the width and height of the face, the proportions of the nose and other features that aren’t affected by the expression on your face or whether you grow a beard or cut your hair-and stores them as a set of numbers known as an eigenface. This is the information stored on the chip in a biometric passport, and it’s compared against the characteristics calculated by the system when you’re photographed at the immigration desk when you return from abroad.

Facial recognition is convenient, because you don’t have to touch or press anything, but facial recognition tools like Visionics FaceIt and Viisage are designed for large corporate systems like identifying ATM users, searching driver license databases, or surveillance. They’re used in casinos, and by some police forces monitoring public areas like beaches.

Recognix claims to do facial recognition with a Webcam. While its FaceCode software works well, recognizing registered faces and rejecting strangers, it hasn’t been updated in two years, and a promised Pro version to work on networked PCs hasn’t appeared. Facial recognition also isn’t the most accurate system for identifying people. It’s used for surveillance because it can be done without suspects co-operating, and it was chosen for passports because it makes people feel less like criminals than more intrusive information-especially if you don’t realize the information is being gathered.