How do I do "wipe" in WinNT

[Werner Koch]

On Tue, 31 Oct 2000, Wesley J Landaker wrote:

> (this does exactly what most utilities like shred do--overwrite with 
> '1's, '0's, and random bytes. Of course, you need a better random 
> source than "rand()" usually, but this should probably be okay 
> anyway--heck, we're using 50 iterations!!!)

The RNG is not the problem - the problem is that all those program
just don't work reliable -  see the recent thread on Bugtraq on the
shred utility.

Shred and also your program assumes that the filesystem alwas
oberwrite existing blocks - this is not always true and it depends on
many paramters to get it right.  The only reliable way to wipe out
files is by using a feature of the filesystem - only the filesystem
and the kernel do know where the bits are really stored and they
must have a facility to overwrite them.

The ext2fs has the "s" attribute (man chattr) to do this - however,
afiak, this is not implemented.

The upshot of this is that you should not assume that a utility like
shred or wipe really does what it indends to do.  It may do it - but
don't count on it.  A more realiable way to do this is by creating a
small partition for plain text files and then do something along the
lines "cat /dev/urandom >/dev/hdxn" - but this is not very
practicable.  The drive itself my also do wierd things.

And for NT you should have a close look at the source (which seems
to be available now in St. Petersburg ;) to decide whether your
utilty has a chance to to what it should do.

  Werner

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