NAND Flash Can Verify a Device's Identity 34
itwbennett writes "Researchers at UC San Diego and Cornell University have developed software that they say can detect variations in flash behavior that are unique to each chip. The system uses 'physically unclonable functions' (PUFs), or variations in manufacturing that are unique to each element of each flash chip. Swanson described one PUF that his team has worked with, called Program Disturb. It uses a type of manufacturing flaw that doesn't affect normal operation but causes problems under test conditions." Related: from last October, another description of such error-based identity assignment.
Properties get more unique as capacity goes up (Score:4, Insightful)
With increasing densities I doubt you have to go so far as to look at program disturb. Even just the distribution of bad cells which are present in all flash chips from the factory happens in a random enough manner to be able to ID each chip. There is no realistic way to be able to duplicate the bad cell pattern either. The only way you could ever hope to do it would be to get a flash chip with no defects (or only a few overlapping ones) and mark extra cells as defective. Feasible for a couple kilobit chip but not possible for gigibit densities.
A better ID system would be DRAM really. Write blanket 0s to a block of the memory and halt the refresh operation, then read it a second or two later and see how many have flipped to 1 and in what pattern (the 0 to 1 flip takes much longer than the 1 to 0 flip so it would be more reproducible).
legal? (Score:4, Insightful)
How long before it's used as evidence in court?