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laextr@icqmail.comquote:Original post by fractoid
I don''t think overwriting with a set pattern (all 1s, then all 0s, or something like that) will actually erase the data to the point where a good lab won''t be able to recover it. As long as they know the pattern, they can actually compensate for that. Bits are analogue on the disk. They aren''t 1 or 0, they''re 0.954 or 0.012. When you write a bit to the disk, a smidgen of the old value gets left there (so writing 1 to a bit with value 0.954 would give you a bit with value 0.958 or something, whereas writing 1 to a bit with value 0.012 would give you 0.905 or something, main point being it''s lower than it woulda been if it was overwriting a 1).
Upshot of all that is that you have to overwrite things a LOT of times (iirc at least 8-16) before they become too munged to untangle. Even then if technology improves it might be possible in 10 or 100 years to recover the data... if what I heard is true, the US government disposes of their sensitive-information-storing hard drives by melting them into slag, stirring them up, chipping them, and then burying them inside concrete blocks in a secure area. Possibly they wrap them in bits of alien spacecraft too.
[edit: of course this is for cases when the government of a high-tech superpower is trying to uncover your plans for a doomsday weapon, and 8192-bit encryption just won''t cut it. If you just want to stop your mommy undeleting your porn collection by mistake, your approach will be fine. ;]
[edited by - fractoid on April 15, 2004 5:55:37 AM]
ICQ Number : 120585863
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laextr@icqmail.comICQ Number : 120585863
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laextr@icqmail.comICQ Number : 120585863
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laextr@icqmail.com