A number of biometrics systems, such as one that analyzes flecks of color in an iris, can be combined to identify a person more accurately than just one alone.

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Those charged with guarding a nation’s borders and critical facilities all share one essential challenge: they want to authenticate the identity of all who pass, minimizing the chance of letting unauthorized persons through (false positives) or of stopping people who are authorized to pass (false negatives).

In addition, checkpoints at airports and customs posts have an equally pressing need: to move people through quickly and avoid long waiting lines.

So what are a nation’s guardians to do? Do they go for accuracy or speed?

Can they have both? The answer could be yes—by combining multiple screening techniques that would, in effect, compensate for each one’s shortcomings.

Ever since the terrorist attacks of 9/11, the use of biometrics—the characterization of human beings based on physiological and behavioral features and traits—has grown. Such techniques are not all new. Photographs and fingerprints have been used for a century. More recently, systems have been devised for measuring the geometry of the palm or hand; recognizing the pattern of blood vessels in a retina or the flecks of color in an iris; or marking the pattern in a person’s DNA. And there are still other techniques, including ones that recognize voices or the way people walk.

LET’S MEET To share infor­mation about the newest advances, the IEEE is cosponsoring the Biometrics Symposium 2007, to be held from 11 to 13 September in Baltimore. Three IEEE groups—the Computational Intelligence Society, the Signal Processing Society, and the Technical Activities Board’s Committee on Bio­metrics—are the symposium’s technical sponsors.

The symposium will feature papers on cutting-edge recognition, identification, and identity-verification methods, such as identifying individuals using electroencephalograms. Among other sessions are ones addressing the securing of identity data by combining encryption with biometrics; the societal and legal implications of biometrics—which addresses privacy and civil liberties concerns; and the development of standard tests for verifying the performance claims of equipment designers and manufacturers.

There are two basic concerns about the technologies used to screen large numbers of people, according to IEEE Fellow Evangelia Micheli-Tzanakou, professor and director of the Computational Intelligence Laboratories at Rutgers University in New Brunswick, N.J. “One is storing and retrieving the data—which only now is becoming less difficult as computers get faster and more capable,” says Micheli-Tzanakou, the IEEE’s liaison to the symposium’s planning committee. “The other is error tolerance—how much you let the machine err in identifying someone.”

MULTIMODAL ATTACK If one biometric measurement is good, how much better are several? The more things measured, the more accuracy can go up. No one technique is good enough on its own.

“The buzzword is multimodal biometrics—authenticating a person’s identity by matching four or five different biometric measurements instead of just one,” says IEEE Senior Member Kostantinos Plataniotis, associate professor of electrical and computer engineering at the University of Toronto. Multimodal biometrics involves security screening that goes beyond a human guard or a machine matching a person’s face to the photograph in, say, a passport. Instead, the person’s iris or retina also might be scanned to see if stored patterns match a given identity, and the inside of a cheek might be scraped for a fast DNA test.

“Each biometric measurement technique has an accuracy problem. It is extremely unlikely, however, that four or five biometric measurements would combine in exactly the same way for the identification of more than one person,” Micheli-Tzanakou explains. Moreover, the different biometrics could cross-check identity in case an aspect of the person changes.

“Face recognition is extremely good, but a person’s face can change surprisingly with illness, diet, or age, as well as with the application of cosmetics, a change in hair color or style, or a suntan,” she continues. “Voice recognition can be temporarily thrown off by congestion from a cold. But again, it is unlikely that four or five biometric measurements would all change at once.”

A number of biometric characteristics can be checked relatively quickly, proponents say. “Gait analysis—observing the periodicity of how someone walks—can be done from a distance, without a person’s knowledge,” Plataniotis says. Placing a hand over a detector to check the geometry of the fingers and palm, speaking into a microphone for a voice check, and pressing a thumb to a sensor to verify a thumbprint are all checks that can be done without long delays.

Last year, several biometric techniques were applied to a new passport introduced by a dozen European Union nations. The passport relies on a photograph taken to exact specifications for machine face recognition, and it also includes a chip that stores biometric data about its owner. Data can be encrypted to prevent identity theft, and the chips can be queried and read from a couple of meters away. Similar chips are also appearing on airline boarding passes.

The hope is that in the future people will simply walk through a security checkpoint while monitoring devices chug away in the background, taking the identifying measurements of their bodies and comparing them with readings on a passport or boarding pass—with little or no delay. Stay tuned.

FOR MORE INFORMATION on the IEEE Biometrics Symposium 2007—which is cosponsored by the Center for Identification Technology Research, a consortium of the (U.S.) National Science Foundation, universities, and industrial companies—visit http://www.citer.wvu.edu/ bsym2007. Information about standards for biometrics can be found at the U.S. National Biometric Security Project at http://www.nationalbiometric.org.