lkml.org 
[lkml]   [1998]   [Jul]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Secure deletion
On Thu, 23 Jul 1998, Alexander Kjeldaas wrote:

> 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.
>

There are always things that "won't work". If your disks are "cleaned"
each night, you will find a high probability that the unwritten data
will contain the security pattern. In fact, since I started using this
technique (two years), I have never seen any unwritten data that
didn't contain (1) The rest of the sector-buffer, (2) The words
"SECURITY" with 8 trailing blanks.


Cheers,
Dick Johnson
***** FILE SYSTEM MODIFIED *****
Penguin : Linux version 2.1.108 on an i586 machine (66.15 BogoMips).
Warning : It's hard to remain at the trailing edge of technology.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.altern.org/andrebalsa/doc/lkml-faq.html

\
 
 \ /
  Last update: 2005-03-22 13:43    [from the cache]
©2003-2011 Jasper Spaans