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Date: Sun, 24 Jul 2005 12:15:36 +1200 From: Volker Kuhlmann <list0570@...adise.net.nz> To: bugtraq@...urityfocus.com Subject: Re: Peter Gutmann data deletion theaory? > Unlike DRAM and SRAM, Flash etc. has no continual or repetitive > amplification function. Traces of previous charges may remain, but I > doubt they would be recoverable, except perhaps by the most drastic > forensic techniques I would expect flash memory content to be easily recoverable when opening the chip. > - and even then, each write or erase operation would > reduce the remnants further still. True, but don't put yourself to rest on it. Ever noticed that flash memory is always smaller than the power of two which it is advertised as? Memory is manufctured in matrices, so where is the missing memory? I suggest these two possibilities: memory blocks coming out of manufacture damaged are "turned off" (prevented from being used), a percentage of memory blocks is reserved for defect management. As everything flash uses a simple sort of FAT filesystem on these memories, the same areas get repeatedly used and worn out, rendering the thing useless very early. As a result, I expect flash memory to have defect management similar to hard disks - when you think you're overwriting it, you're in reality writing elsewhere. For either flash or hard disk you'll need to get past internal defect management to sanitise the data. Or physically destroy the memory media - always safest. Volker -- Volker Kuhlmann is possibly list0570 with the domain in header http://volker.dnsalias.net/ Please do not CC list postings to me.
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