A group led by a Princeton University computer security researcher has developed a simple method to steal encrypted information stored on computer hard disks.

The technique, which could undermine security software protecting critical data on computers, is as easy as chilling a computer memory chip with a blast of frigid air from a can of dust remover. Encryption software is widely used by companies and government agencies, notably in portable computers that are especially susceptible to theft.

The development, which was described on the group’s Web site Thursday, could also have implications for the protection of encrypted personal data from prosecutors.

The move, which cannot be carried out remotely, exploits a little-known vulnerability of the dynamic random access, or DRAM, chip. Those chips temporarily hold data, including the keys to modern data-scrambling algorithms. When the computer’s electrical power is shut off, the data, including the keys, is supposed to disappear.

In a technical paper that was published Thursday on the Web site of Princeton’s Center for Information Technology Policy, the group demonstrated that standard memory chips actually retain their data for seconds or even minutes after power is cut off.

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