Two years ago, the Department of Homeland Security stepped up its campaign to install controversial body scanners at airports nationwide. At the time, the agency claimed the machines could spot all sorts of hidden weapons and contraband. Today, more than 700 of the imagers are in place at 180 airports. But the so-called "naked" scanners may not be quite as all-seeing as they were originally billed to be. Quietly, DHS has called in the Pentagon's premier research agency to help develop a new generation of imagers that are faster, smaller, more precise, and less prone to hacking.

It's a bit of a shift for Darpa, which is usually asked to tackle the military's toughest research problems: machines that can think, satellites that can assemble themselves in space, networks that can't be pwned. And it underlies just how difficult it can be to quickly screen millions and millions of people for a few concealed threats.

In an announcement published Monday, the DHS and Darpa indicated that the research for improved body scanners will focus on two main features. The first is defined as "real-time utilization of compressive measurement techniques." Its benefits will be faster acquisition of images with fewer samples, scanners equipped with less hardware and, most importantly, more precise and reliable detection with "reduced probability of false alarm."

"The research seeks to identify novel signatures distinct from those typically employed in conventional X-ray tomography systems and multi-view dual energy projection scans," the agencies explain.

The second focus will be on secure memory chips. These will have to be "hack-proof" chips with "high-levels of functionality ... for low-cost, reduced power consumption and increased reliability." The DSH and Darpa want high-speed chips, with random access times "on the order of 10 ns [nanoseconds]." They should also have "extremely high-endurance," which would allow for "near unlimited wear for write, read, and erase cycles." To be really un-hackable, they should be resistant to off-line security attacks as well. Stored data shouldn't be readable with powerful devices like electron or atomic force microscopes.

Despite controversies around their intrusiveness, current naked body scanners were widely adopted in 2010 after a terrorist failed to detonatehis "underwear bomb" on a plane headed to Detroit. Since then, claims about the scanners' capabilities have, at times, been overblown by privacy activists and by the media. The ACLU stated at the time that scanners produce "strikingly graphic images of passengers' bodies, essentially taking a naked picture." DHS and the Transportation Security Agency has let the talk go on, conscious that scary capabilities – however untrue – work as a good deterrent.

When they were rolled out, full body scanners have been criticized for violating traveler's privacy. Backscatter X-ray scanners, one of the two types used by the TSA, basically allowed officers to see under somebody's clothes. For privacy advocates like the ACLU, that was just like a "virtual strip search," which would be prohibited when there's no probable cause. Some of these concerns have been alleviated with the adoption of new software that displays passengers as generic stick figures.

There have been health concerns, as well. For some, the use of X-rays could have dangerous consequences. Radiation safety authorities, however, have stated that there's no evidence that supports the notion that full X-ray body scanners could have health risks. Not only that, according to the American College of Radiology, "an airline passenger flying cross-country is exposed to more radiation from the flight than from screening by one of these devices."

On Sept. 18, DHS and Darpa will hold at meeting with researchers in Arlington, Virginia, about a next generation of scanners. A strategy to enhance the detection of explosives in both checked baggage and checkpoint screening will be presented, as will Darpa's Knowledge Enhanced Compressive Measurement program, whose goal is to develop systems that gather high-quality information without high-quality instruments. Darpa thinks it could revolutionize traditional sensor systems.

Of course, it's way too early to tell whether another generation of airport scanners will really make flying any safer. But it's worth noting that the TSA is trying to inch away from mass-screening, and toward an approach that concentrates only on the most likely terror suspects. So far, these results have been mixed, at best; a pilot project at Logan Airport resulted in TSA employees harassing black and Latino travelers. Perhaps by the time these new scanners come online, the TSA's so-called "intelligence-driven" approach will be a little smarter.