From: landon dyer <landon@best.com>
Date: Thu, 8 Oct 1998 07:56:35 +0800
To: Steve Dunlop <nospam@bitstream.net>
Subject: Re: NT 5.0 and EFS -- A victory for widespread use of crypto?
In-Reply-To: <361BF3ED.8111C033@bitstream.net>
Message-ID: <3.0.3.32.19981007164728.009611c0@shell9.ba.best.com>
MIME-Version: 1.0
Content-Type: text/plain



At 06:06 PM 10/7/98 -0500, you wrote:
>
>Does anyone have any opinions on the encrypting file
>system (EFS) that is supposed to ship with NT 5.0?

  you're asking the *cypherpunks list* if anyone has
an opinion?  oh, gad...  :-)


>EFS appears to have the architecture to support
>arbitrarily long keys although this has been crippled
>in the NT5.0 release, presumably because of
>export limitations.  It has the key recovery features
>you would expect in a commercial product of the
>type; they can be turned off administratively.


  excerpted (without permission) from the latest issue of the
microsoft systems journal, about the new feature of NTFS in
NT 5.0, specifically regarding encryption:

  "...NTFS has built-in recovery support so that the encrypted
   data can be accessed.  In fact, NTFS won't allow files to be
   encrypted unless the system is configured to have at least
   one recovery key.  For a domain environment, the recovery keys
   are defined at the domain controller and are enforced on all
   machines within the domain...."

  i'll definitely have to play with this one -- wh'appens if you add
a machine to a domain, encrypt some files, then remove the machine
from the domain?  can the admin of the domain recover all files
you encrypt from that point on?  and so on...


  "...For home users, NTFS automatically generates recovery keys
   and saves them as machine keys.  You can then use command-line
   tools to recover data from an administrator's account."


  if i were looking for a point of attack, i'd start with the
low-level key management here...


  another interesting thing to try: install NT on a workstation,
encrypt a removable disk, then reinstall NT on that workstation
again -- have you defeated key recovery for that disk?  (since the
machine keys for the first install of NT are presumably gone...)


-landon (re-lurking)