[Cryptography] Shredding a file on a flash-based file system?

[Jerry Leichter]

On Jun 20, 2014, at 5:24 AM, Joseph Ashwood <ashwood at msn.com> wrote:
> Even at the flash chip level, each layer in the flash chip often has its own wear leveling going on, this is done in order to disguise that the chip has flaws, in any high capacity chip there are many sectors that are unusable straight from the factory.
You can these days buy USB sticks with capacities anywhere from 4GB (maybe there are still some smaller ones) to 128GB or even more.  You pay by capacity - generally 50 cents to a dollar a GB these days.  It's not that the chip makers are making a whole range of different sized NVRAM's.  Rather, they make "the largest they can" accepting a high rate of bad cells, and simply put them in different bins depending on how much of that memory shows up as working.  That the prices per bit are more or less constant (except at the very high end) tells you something out the yield curves....

The same thing as the CPU makers do with speed binning, but on a much larger scale over bins that span a much larger range.
                                                        -- Jerry

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