Re: Hard Drive Destruct System?

From: Walter Roberson (roberson_at_ibd.nrc-cnrc.gc.ca)
Date: 11/28/04 

Date: 28 Nov 2004 08:52:02 GMT

In article <coas47$ijt$1@panix5.panix.com>, Al Dykes <adykes@panix.com> wrote:
|In article <coaok5$eb0$1@canopus.cc.umanitoba.ca>,
|Walter Roberson <roberson@ibd.nrc-cnrc.gc.ca> wrote:

|>In practice, you can't use a single encryption over a whole drive,
|>because you have to be able to randomly read or wrote from the middle of
|>it without having to decrypt everything before that point (read) or
|>re-encrypt everything after that point (write.) And directory structures

|Offhand I can't see any problem with en/decrypting data in 512 byte
|blocks as sectors are read/written to disk.

If you are using the same key each time, that scheme would suffer
a lot from "known plaintext" attacks. For example,
All blocks of NULLs would encrypt exactly the same way, and
the first 64 bytes of most non-text files would be relatively
consistant amongst filetypes, allowing you a fairly good idea
of what kind of file something was without decrypting it. 

-- 
Is "meme" descriptive or perscriptive? Does the knowledge that
memes exist not subtly encourage the creation of more memes?
   -- A Child's Garden Of Memes
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