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(Chip Somodevilla/2009 Getty Images)
(Chip Somodevilla/2009 Getty Images)

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That naked image at airport security actually enhances your privacy Add to ...

As a result of the attempted Christmas Day bombing, the U.S. Transportation Security Administration, the Canadian Air Transport Security Authority and other agencies have been hurrying to implement a new technology for airport security. The "back-scatter" X-ray provides naked images of passengers - but in a way that increases airport security and protects privacy.

The millimetre-wave X-ray is a better mousetrap: It uses low-energy X-rays (1/10,000th of a cellphone emission) to detect metal, liquids, drugs and other contraband. In test images I have seen, coins, belt buckles, BlackBerrys, knives, drugs and explosives pop out of the screen: bright white on a grey outline. The scanner provides front and back images of the traveller in remarkable detail, seeing right through clothing.

This system has already been tested at airports in Phoenix, Miami, Los Angeles and New York and will be rolled out at more in the coming months. The American tests found that frequent fliers were excited to use the technology: It is much faster than the combination of metal-detector archway, hand-wand search and physical pat-down. If you know how to empty your pockets, this is going to make going through airport security much quicker.

The X-ray archways we walk through today were invented in the 1970s to detect metal. We've all set off the alarm with a belt buckle, coin or underwire bra. Unfortunately, plastic guns, ceramic knives, explosive underpants and liquid all escape detection.

Security analysts have sarcastically suggested that the only way to ensure aviation security is to fly naked. But the new technology gives the best possible security screening of passengers and several system tools to protect passengers' privacy. It may be difficult to see how an X-ray that strips your clothes for a screening officer protects your privacy, but there are four crucial parts of the system that provide security and ensure that privacy invasion is minimal.

First, the image screening officer (ISO) is totally separated from the screening line. There is no way for the ISO to connect the naked image with a clothed person - it is a different part of the airport entirely. In the same way that radiologists and other image analysts see images from patients, these ISOs will examine hundreds of images but not interact with the actual people. No personal or identifying information is ever connected to that image.

Second, the images are not recognizable as particular individuals. I could not distinguish facial features from the scans I have seen. So, even if I was looking for someone going through a screening point, I couldn't identify which of the hundreds of images was that individual (unless he or she had a really striking physical characteristic). There is no need to smile, because facial features are not visible (which also means ethnicity, national background, language and behaviour are also not visible).

Third, the image on the screen cannot be saved, printed or transmitted. The image stays on the screen until the passenger has been cleared and then is erased from memory.

Finally, the detailed image is not transmitted to the screening officer at the checkpoint. A stick figure is displayed to the officer that indicates the area of the alarm. It is then his/her responsibility to find the item through the normal pat-down procedure.

Let me be controversial by saying the millimetre-wave scanner actually enhances privacy. The only way for a screening officer to raise an alarm about a passenger is based on an item detected in the body image. The ISO cannot make a decision based on any kind of explicit profile or unconscious stereotype. We trade an abstract, unrecognizable naked photo of ourselves and in return get a much more secure airport. The isolated screening officer signals the alarm, but the screening officer in front of us simply has a stick figure that highlights the area that caused the alarm. We can detect a host of prohibited items that are now invisible to the system.

If the public can be persuaded to use this technology, it has the potential to increase both the speed and the reliability of airport screening. The question is: Will Canadians be willing to fly naked?

Mark Salter, an associate professor at the University of Ottawa's School of Political Studies, is the editor of Politics at the Airport.

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