The Myth of Microsoft Security


Robert Novak Hypes "Microsoft's Powerful Codes"

Buzzwords, by J. Orlin Grabbe

The News

The "NSA Backdoor" in Microsoft Windows

The Story Behind the Sound and Fury


Analysis By People We Trust I: Markus Kuhn

Subject: Re: NSA key in MSFT Crypto API
Date: Sat, 04 Sep 1999 11:41:02 +0100
From: Markus Kuhn 
To: "cypherpunks@Algebra. COM" ,
     "'Salz, Rich'" ,
     "Cryptography@C2. Net" ,

The actual funny story behind the presence of the NSA key has been
seriously misunderstood here. CSP verification keys have only one *real*
purpose: They are intended to enforce the US export restriction
requirement that Microsoft is not allowed to ship software abroad that
can easily be extended with strong cryptography. They are certainly not
intended as any useful form of integrity protection for your system.

The NSA got their own CSP verification key, because they want to be able
to change their own secret US government CSPs required for the handling
of classified documents, without having to go to Microsoft each time to
get a signature for an NSA CSP update. Fair enough. So Microsoft built
in a second verification key such that the NSA can produce and install
on DoD PCs their own CSPs without requiring any Microsoft involvement.

The real funny part is that Microsoft did not protect the NSA key
particularly well, such that everyone can easily replace the NSA key
easily with his own key. This was reported by Nicko van Someren at the
Crypto'98 rump session. This means that everyone can now easily install
his own CSPs with arbitrarily strong cryptography. This means that the
NSA's demand to get quickly a second key added led in effect to the easy
international availability of strong encryption CSPs. My guess is that
this is Microsoft's sweet revenge against the NSA for creating all these
Export hassles (e.g., the requirement that CSPs be signed) in the first
place. It backfired nicely against the NSA. :)

All this has nothing to do with an NSA backdoor, because the CSP keys
are an export enforcement tool and not an integrity protection tool.
They do not protect all parts of the system that could be compromised by
someone who wants to install some eavesdropping malware. The CSP
verification keys only authenticate that no cryptography that violates
export laws has been installed. If you are worried about the NSA
installing malicious software on your PC, you should not rely on the CSP
verification keys (which were never designed for that purpose anyway),
but on virus scanners with tripwire functionality that report any
modifications to your DLLs. There is no digital signature functionality
required to implement these, simple secure hash algorithms will
perfectly do.

Please apply a bit of simple critical thinking here:

If the NSA wanted to have real backdoor functionality, they would much
more likely simply steal Microsofts own keys instead of embedding
additional keys with an obvious symbol name. Remember: The NSA is the
world's largest key thief. They have stolen crypto variables from
well-protected military and government agencies from all over the world
using the usual repertoire of techniques (bribery, extortion,
eavesdropping, hacking, infiltration, etc.). If they can do it with
eastern military agencies, they can most certainly also do it easily
with Microsoft, which is orders of magnitudes less well protected than
the usual NSA target. If there is a real NSA backdoor key in Windows,
that it would certainly be identical to Microsoft's own key.


Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at,  WWW: 


Analysis By People We Trust II: Bruce Schneier

from: sci.crypt
subject: NSA and MS windows

A few months ago in my newsletter Crypto-Gram, I talked about
Microsoft's system for digitally signing cryptography suits that go
into its operating system.  The point is that only approved crypto
suites can be used, which makes thing like export control easier.
Annoying as it is, this is the current marketplace.

Microsoft has two keys, a primary and a spare.  The Crypto-Gram
article talked about attacks based on the fact that a crypto suite
is considered signed if it is signed by EITHER key, and that there
is no mechanism for transitioning from the primary key to the
backup.  It's stupid cryptography, but the sort of thing you'd
expect out of Microsoft.

Suddenly there's a flurry of press activity because someone notices
that the second key is called "NSAKEY" in the code.  Ah ha!  The NSA
can sign crypto suites.  They can use this ability to drop a
Trojaned crypto suite into your computers.  Or so the conspiracy
theory goes.

I don't buy it.

First, if the NSA wanted to compromise Microsoft's Crypto API, it
would be much easier to either 1) convince MS to tell them the
secret key for MS's signature key, 2) get MS to sign an
NSA-compromised module, 3) install a module other than Crypto API to
break the encryption (no other modules need signatures).  It's
always easier to break good encryption.

Second, NSA doesn't need a key to compromise security in Windows.
Programs like Back Orifice can do it without any keys.  Attacking
the Crypto API still requires that the victim run an executable
(even a Word macro) on his computer.  If you can convince a victim
to run an untrusted macro, there are a zillion smarter ways to
compromise security.

Third, why in the world would anyone call a secret NSA key "NSAKEY."
Lots of people have access to source code within Microsoft; a
conspiracy like this would only be known by a few people.  Anyone
with a debugger could have found this "NSAKEY."  If this is a covert
mechanism, it's not very covert.

I see two possibilities.  One, that the backup key is just as
Microsoft says, a backup key.  It's called "NSAKEY" for some dumb
reason, and that's that.

Two, that it is actually an NSA key.  If the NSA is going to use
Microsoft products for classified traffic, they're going to install
their own cryptography.  They're not going to want to show it to
anyone, not even Microsoft.  They are going to want to sign their
own modules.  So the backup key could also be an NSA internal key,
so that they could install strong cryptography on Microsoft products
for their own internal use.

But it's not an NSA key so they can secretly install weak
cryptography on the unsuspecting masses.  There are just too many
smarter things they can do to the unsuspecting masses.

My original article:


Nice analysis:

Useful news article:
** Bruce Schneier, President, Counterpane Systems    Phone:
612-823-1098 101 E Minnehaha Parkway, Minneapolis, MN  55419
Fax: 612-823-1590           Free crypto newsletter.  See:

Posted Sept. 4, 1999
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