Re: Secure deletion

Alexander Kjeldaas (astor@guardian.no)
Thu, 23 Jul 1998 18:59:00 +0200

On Thu, Jul 23, 1998 at 09:14:44AM -0400, Richard B. Johnson wrote:
>
> If you don't need 'instantaneous' security, i.e., you can clean up
> your disk(s) once a day, just make a program that writes a file,
> filled with "SECURITY ", until the disk partition is full.
> Close the file, sync the file-system, then delete the file.
>

This probably won't work for a block that has been reused in another
file, but where the whole block hasn't been overwritten by the new
file. Let's say I have a 100k file, delete it and create 100 1-byte
files which occupies the blocks from the 100k file (blocksize 1k).
Then there will be 1023 bytes in each block which are allocated, but
with unknown state. Whether they are overwritten by 0s or not written
at all is unspecified.

astor

-- 
 Alexander Kjeldaas, Guardian Networks AS, Trondheim, Norway
 http://www.guardian.no/


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