Tuesday, December 05, 2006

Superman Works for Airport Security Now

I've had occasion to mention Superman before ("Sniffing Through Your Wallet with RFID", Oct. 25, 2006), but my reference then to his X-ray vision was in jest. Well, a news item from the U. S. Transportation Security Administration says that in effect, they've hired Superman (at least, the mechanical equivalent of his X-ray vision ability) to watch passengers at Phoenix's Sky Harbor International Airport. The effect is to allow strip searches without stripping.

According to the Dec. 1 Associated Press news item, in the initial tests of the system, which uses a type of X-ray technology called "backscatter," security officials will examine only people who fail the primary screening. These passengers will be offered the choice of either a pat-down search or examination by the backscatter machine. The images, which reportedly are blurred by software in "certain areas," are nevertheless detailed enough to show items as small as jewelry next to the body. The technology is already in use in prisons, and the intensity of X-rays is much lower than a typical medical X-ray.

When I read this story, it brought back memories of my days as a junior terrorist. Before you get up from your computer to call the FBI, let me explain. In the 1990's, I did some consulting work for a company that was developing a contraband detection system using short radio waves called millimeter waves. It turns out that the human body emits these waves just because it's warm. With a detector that is sensitive enough, you can detect the waves coming through clothing, and if you are wearing something like plastic explosive under your shirt, the shadow of it will show up in the image.

We built a system, and to test it, several of us took turns playing terrorist by wearing lumps of modelling clay and plastic pistols taped to our shirts underneath a windbreaker. It was a tedious task, because the machine took 15 minutes or more to make a decent picture and you had to hold still the whole time. The results looked like blurry photographic negatives, but you could see the outlines of the contraband clearly. You could also see the main features of the body underneath the clothing, and that led to some privacy concerns, as you might imagine. The wife of the company president volunteered to be our female subject. I never saw the resulting picture—apparently it was detailed enough to be censored. For a number of reasons, both technical and social, that particular machine never made it to market, but all this was before 9/11 and the sea change in our attitudes toward airport security that resulted.

This change in attitudes has done funny things to some people, notably Susan Hallowell, who is the Transportation Security Administration's security laboratory director. A picture accompanying the article shows Ms. Hallowell in the X-ray altogether, and shows about the same detail as a department-store mannequin from the 1950s, or a Barbie doll. I suppose Ms. Hallowell's willingness to pose was motivated by a sincere desire to increase the quality of airport security with less discomfort to passengers, but it wouldn't surprise me if her strategy backfires. If I put myself in the mindset of a middle-aged woman who faces the choice of either letting another woman do a pat-down search, or knowing that somewhere out of sight, somebody—possibly another woman but possibly not—is going to see every single bulge, sag, and fold underneath my clothes, I would choose the pat-down search every time. In fact, I'd go screaming to my Congressman to stop implementation of the backscatter system before my naked profile showed up on MySpace. Yes, the TSA says the images won't be stored or transmitted. And maybe they will be able to keep that promise. But if there's a leak somewhere—say Madonna goes through one of these things and a paparazzi manages to bribe an inspector—the whole plan could go up in political flames.

Besides which, there is a principle that is largely neglected today, but still deserves some attention: the Constitutional prohibition against unreasonable searches and seizures. The Fourth Amendment says in full, "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized." I'm no Constitutional or legal scholar, and obviously some legal means has been found to get around constitutional challenges to airport security inspections. Probably the argument is, if you don't want to be searched, take the bus. But letting somebody I don't know see me without clothes, simply on the slight chance that I'm carrying a gun or a bomb, seems to cross a line that we as a nation have hesitated to cross before.

When George Orwell portrayed the ever-present unblinking eye of Big Brother in his dystopia 1984, the idea of being spied on constantly had the power to shock, because it was so novel. But today there are places in England where you can walk for many blocks and never be out of sight of security cameras. This has not destroyed England, and it has actually helped track down terrorists such as those who committed the London subway bombings. The thing we lose when one more privacy barrier comes down is so hard to describe because it's silent, has no public relations agent promoting it, and doesn't show up in the compilation of gross national products. But it's the kind of thing that you notice mainly after it's gone. And once it goes, it can be very hard to recover.

Sources: The AP article describing the Phoenix tests was carried by many media outlets, among them MyWay (http://apnews.myway.com/article/20061201/D8LO1JLO2.html). The paper describing my foray into contraband detection was entitled “Contraband detection through clothing by means of millimeter-wave imaging,” by G. R. Huguenin et al., SPIE Proc. 1942 Underground and Obscured Object Imaging and Detection, Orlando, FL, pp. 117-128, 15-16 April 1993.

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