Machine Design

Bye, bye data

When a U.S. intelligencegathering-aircraft was involved in a midair collision off the coast of China four years ago, the crew couldn't erase sensitive information from magneticdata-storage systems before making an emergency landing in Chinese territory.

Georgia Tech Research Institute Research Engineer, David Maybury, models a magnetic-data-destruction circuit using 3D finite-element analysis. Georgia Tech photo: Gary Meek

This event underscored the need for a simple way to positively destroy sensitive data aboard such aircraft. Working with defense contractor L-3 Communications Corp., New York City, scientists at the Georgia Tech Research Institute (GTRI) have developed prototype systems incorporating special, high-strength permanent magnets that quickly erase a wide variety of storage media.

Researchers also looked at alternative destruction techniques, including burning diskettes with heat-generating thermite materials, crushing drives in presses, and chemically destroying the media. None of these techniques was considered safe or practical for use in aircraft, so this left only magnetic erasure.

"We had to verify that data would be beyond all possible recovery, even with unlimited budget and unlimited time," explains Michael Knotts, a research scientist in the GTRI's Signature Technology Laboratory. "Existing devices lack sufficient magnetic strength, are too large and heavy, or don't meet stringent air-safety standards."

Part of the project involved developing testing procedures that use a magnetic-force microscope (MFM). An MFM maps the tiny magnetic perturbations created by stored data, and helps determine how well data patterns have been destroyed. A random distribution of magnetization on the media indicates a clean, datafree disk.

Researchers cut a number of commercially available microdrives into sections, put them in varying magnetic fields, and tested the sections with the MFM. It turns out custom neodymium iron-boron magnets and pole pieces of cobalt alloys produce enough of a magnetic field to destroy data patterns. The magnets, which weigh about 125 lb, produce magnetic fields comparable to those in magneticresonanceimaging equipment, necessary to penetrate metallic housings that surround some drives.

How to apply the magnetic field to the storage media is another challenge. In some cases, aircraft crews would simply insert removable media into a motorized mechanism that pushes them past the magnets, while for other media, drives are removed from enclosures and passed through a magnetic field. Each technique involves several deliberate steps designed to prevent accidental erasure. The final phase of the project will involve erasure of data on large computer hard drives partially encased in thick steel caddies.

L-3 Communications Corp.,

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