From: Sergey Goldgaber <sergey@delbruck.pharm.sunysb.edu>
Date: Wed, 23 Feb 94 16:26:05 PST
To: cypherpunks@toad.com
Subject: Re: STEALTH OCEANS
Message-ID: <Pine.3.89.9402231907.A2008-0100000@delbruck.pharm.sunysb.edu>
MIME-Version: 1.0
Content-Type: text/plain


This is my first post to this list, so please don't flame me if I make
some trivial mistake. %->


IDEA Re: making random noise files "undetectable"...
~~~~~~~  On many machines the file system allows users to "delete" files
         without actually deleting them.  This is usually accomplished by
         simply marking the disk blocks that make up the file as free.
         Thus it should be possible to write an encrypted (noise) file on 
         to disk, pad the rest of the disk with more noise and "delete" the
         whole thing, making the disk look blank to all casual observers.

PROBLEM: If the above idea is implemented, one could not write on to the
~~~~~~~  the disk for fear of accidentaly overwriting the "free" disk blocks.

SOLUTION: Knowing the _exact_ location and size of the file, one could write 
~~~~~~~~  directly to those block which are _really_ free.

2nd PROBLEM: In order to decrypt the file, one needs to know it's 
~~~~~~~~~~~  _exact_ location and size (or use some undelete util)...
             Which brings me to the...

3rd PROBLEM: An undelete utility could make recovering the encrypted
~~~~~~~~~~~  file trivial for _anyone_.

SOLUTION: Make the file undetectable to udelete utilitys by modifying
~~~~~~~~  the FAT table, or equivalent.  One would, of course, have to keep
          track of the file in some other, non-standard, way.

FINAL(?) PROBLEM: Implementing the above idea is trivial for the average
~~~~~~~~~~~~~~~~  user.  Making and recovering truely undetectable files 
                  may not be.


                                 All feedback welcome,

                                     Sergey


PS:  I originally posted this message on Feb. 18, '94
        I am now reposting in hope of recieving more feedback from other 
        readers.

PPS:  Please forgive me for my previous repost.  I just realized it is
          illegible to anyone without MIME.