[117474] in Cypherpunks
Re: A-M$: The Microsoft NSA Back Door. (fwd)
daemon@ATHENA.MIT.EDU (David Wagner)
Fri Sep 3 20:10:47 1999
To: cypherpunks@cyberpass.net
From: daw@cs.berkeley.edu (David Wagner)
Date: 3 Sep 1999 16:29:17 -0700
Message-ID: <7qplkd$nu8$1@blowfish.isaac.cs.berkeley.edu>
Reply-To: daw@cs.berkeley.edu (David Wagner)
In article <Pine.LNX.4.10.9909032217220.5420-100000@zor.hut.fi>,
Zombie Cow <waste@zor.hut.fi> wrote:
> It turns out that every copy of Windows 95, 98, NT 4, and Windows 2000
> has a back door that makes it easy for the National Security Agency to
> gain access to your computer.
Sigh. I fear you are misinterpreting the discovery -- you might want to look
closer at the technical details. I've been trying to urge caution to the
reporters who've called me about it. This does NOT appear to be a case of the
NSA installing a backdoor that lets them spy on Windows machines around the
world.
I should explain. To load a new crypto module into Windows, it must be signed
with Microsoft's key; to get a signature from MS, you have to go through this
whole rigamarole (export controls....). The discovery is that there's a
second, mysterious, alternative key that can be used to load a crypto module
into Windows. On one platform, MS folks forgot to strip out debugging symbols,
and the key can be seen to bear the suggestive label "_NSAKEY".
So, at worst, this is a backdoor that allows that NSA to manage their own
computers more easily, without going through the rigamorole that the rest of
us have to deal with. This is, IMHO, a lesser sin (albeit still an abuse of
export controls, if true).
Also, there is some question whether this key actually belongs to the NSA.
One reporter I spoke to said she talked to Microsoft, and they claim that it
is just a backup key (in case they lose the private key corresponding to the
first one?), and is not a backdoor for the NSA. Their response is weasel
worded carefully enough that I do not trust it 100%, but I'd urge everyone to
check further with Microsoft before drawing any final conclusions.
The discovery _does_ have some security implications: The discovery makes it
easier to bypass the controls on loading new crypto modules. There seems to
be some "software tamper-proofing" (heh) in place that causes Windows to crash
if you try to alter the main Microsoft key, but you can alter the "_NSAKEY"
without any difficulties.
Thus, the next Melissa virus could incorporate code that changes the "_NSAKEY"
and downloads a Trojaned crypto module into your machine.
Ironically, the biggest impact of the "_NSAKEY" may be that it will make it
easier to bypass Microsoft's export controls on crypto modules. In the future,
third-party release of crypto modules may include code that, during the
installation process, changes the "_NSAKEY" to authorize downloading of new
strong crypto modules; this will make it possible for the first time for
foreign crypto developers to write code that upgrades international versions
of Windows to full-strength crypto.
