- NSAKEY
_NSAKEY is a variable name discovered in
Windows NT 4 Service Pack 5 (which had been released unstripped of its symbolic debugging data) in August1999 by Andrew D. Fernandes ofCryptonym Corporation . That variable contained a 1024-bitpublic key .Overview
Microsoft 's operating systems require all cryptography suites that can go into its operating systems to have a digital signature. When only Microsoft-approved cryptography suites can be used, complying with theExport Administration Regulations (EAR) of theUS Department of Commerce ,Bureau of Export Administration (BXA) (now known as the Bureau of Industry and Security or BIS) is easier. It was already known that Microsoft uses two keys, a primary and a spare, either of which can create valid signatures. The primary key is stored in the variable _KEY; Fernandes had discovered the second key.Fernandes published his discovery, touching off a flurry of speculation and development of numerous conspiracy theories. If the private half of that key were actually owned by the United States
National Security Agency , the NSA (as suggested by the name), it would allow that intelligence agency to subvert any Windows users' security.In addition, Windows 2000 had a third key with an unknown purpose, found by Dr. Nicko van Someren. [cite web |title=Microsoft, the NSA, and You |publisher=Cryptonym |date=1999-08-31 |url=http://web.archive.org/web/20000617094917/http://www.cryptonym.com/hottopics/msft-nsa/msft-nsa.html |accessdate=2007-01-07 (
Internet Archive / Wayback Machine)] Microsoft claims this is only in beta builds of Windows 2000 and that its use was for signingCryptographic Service Provider s. [cite web |title=There is no "Back Door" in Windows |publisher=Microsoft |date=1999-09-07 |url=http://www.microsoft.com/technet/archive/security/news/backdoor.mspx?mfr=true |accessdate=2007-01-07] It did not have any clear purposes according to van Someren, [cite web |title=How NSA access was built into Windows |publisher=Heise |date=1999-01-04 |url=http://www.heise.de/tp/r4/artikel/5/5263/1.html |accessdate=2007-01-07] and it is unclear whether it is present in final builds or just beta builds. ( [http://web.archive.org/web/20061124104925/www.microsoft.com/technet/archive/security/news/backdoor.mspx There is no 'Back Door' in Windows] conflicts with [http://web.archive.org/web/20000816181539/http://www.cryptonym.com/hottopics/msft-nsa/msft-nsa.html Microsoft, the NSA, and You] and [http://www.heise.de/tp/r4/artikel/5/5263/1.html How NSA access was built into Windows] )Microsoft's reaction
Microsoft, however, denied all such suggestions. "This report is inaccurate and unfounded. The key in question is a Microsoft key. It is maintained and safeguarded by Microsoft, and we have not shared this key with the NSA or any other party." [cite press release|title=Microsoft Says Speculation About Security and NSA Is "Inaccurate and Unfounded"|publisher=Microsoft Corp.|date=1999-09-03|url=http://www.microsoft.com/presspass/press/1999/sept99/rsapr.mspx|accessdate=2006-11-09] The key's symbol was "_NSAKEY" because the NSA is the technical review authority for U.S. export controls, and the key ensures compliance with U.S. export laws.
The Computers, Freedom and Privacy 2000 (CFP2000) conference was held from 4-
7 April 2000 inToronto ,Canada . During a presentation to that conference, Duncan Campbell, Senior Research Fellow at theElectronic Privacy Information Center (EPIC), mentioned the _NSAKEY controversy as an example of an outstanding issue related to security and surveillance.Richard Purcell, Microsoft’s Director of Corporate Privacy, approached Campbell after his presentation and expressed a wish to clear up the confusion and doubts about _NSAKEY. Immediately after the conference, Scott Culp, of the Microsoft Security Response Center, contacted Campbell and offered to answer his questions. Their correspondence began cordially but soon became strained; Campbell apparently felt Culp was being evasive and Culp apparently felt that Campbell was hostilely repeating questions that he had already answered. On
28 April 2000 , Culp stated that "we have definitely reached the end of this discussion ... [which] is rapidly spiraling into the realm of conspiracy theory" [cite web |title=The Culp-Campbell correspondence (Microsoft Stonewalls _NSAkey Questions) |publisher=Cryptome |date=2000-05-25 |url=http://cryptome.org/nsakey-ms-dc.htm |accessdate=2006-11-27] and Campbell's further enquiries went unanswered.Explanations from other sources
After a great deal of discussion featuring wildly varying levels of cryptographic expertise, various conclusions have been presented. To begin with, some observers, including Fernandes, doubt the BXA's EAR have specific requirements for backup keys. However, none of the commentators claim the legal expertise necessary to authoritatively discuss that document.
Microsoft insists that the second key is present as a backup to guard against the possibility of losing the primary secret key. Fernandes and
Bruce Schneier both doubt this explanation, pointing out that the generally accepted way to guard against loss of a secret key issecret splitting , which would divide the key into several different parts, which would then be distributed throughout senior management. [cite web |title=Analysis by Bruce Schneier |publisher=Counterpane |date=1999-09-15 |url=http://www.schneier.com/crypto-gram-9909.html#NSAKeyinMicrosoftCryptoAPI |accessdate=2007-01-07] Such a plan would be far more robust than simply using two keys; if the second key is also lost, Microsoft would need to patch or upgrade every copy of Windows in the world, as well as every cryptographic module it has ever signed.On the other hand, if Microsoft failed to think about the consequences of key loss and created a first key without using
secret splitting (and did so in secure hardware which doesn't allow protection to be weakened after key generation), and theNSA pointed out the problem as part of the review process, it might explain both why Microsoft weakened their scheme with a second key and why the new one was called _NSAKEY. (The second key might be backed up usingsecret splitting , so losing both keys needn't be a problem.)Another line of speculation concludes that Microsoft included a second key to be able to sign cryptographic modules outside the United States, while still complying with the BXA's EAR. If cryptographic modules were to be signed in multiple locations, using multiple keys is a reasonable approach. However, no cryptographic module has ever been found to be signed by _NSAKEY and Microsoft denies that any other certification authority exists.
A third possibility is that the _NSAKEY enables the NSA or other agencies to sign their own cryptographic modules without being required to disclose those modules to Microsoft, which would allow them to create modules in-house that implement classified algorithms. Of course this capability would also enable an agency to sign modules that could be used to undermine the security of any Windows installation. Such speculation is usually followed by cynical comments on such undermining not being difficult even without access to the cryptographic API.Fact|date=August 2007
Microsoft denies that the NSA has access to the _NSAKEY secret key.
The key is still present in all versions of Windows, though it has beenrenamed "_KEY2."
It is possible to remove the second, _NSAKEY using the following:
There is good news among the bad, however. It turns out that there is a flawin the way the "crypto_verify" function is implemented. Because of the way thecrypto verification occurs, users can easily eliminate or replace the NSA keyfrom the operating system without modifying any of Microsoft's originalcomponents. Since the NSA key is easily replaced, it means that non-UScompanies are free to install "strong" crypto services into Windows, withoutMicrosoft's or the NSA's approval. Thus the NSA has effectively removed exportcontrol of "strong" crypto from Windows. A demonstration program that replacesthe NSA key can be found on Cryptonym's website. [cite web |title=Microsoft, the NSA, and You |publisher=Cryptonym |date=1999-08-31 |url=http://web.archive.org/web/20001109204800/http://www.cryptonym.com/hottopics/msft-nsa/msft-nsa.html |accessdate=2007-01-07 (
Internet Archive / Wayback Machine)]CAPI Signature Public Keys as PGP Keys
In September
1999 , an anonymous researcher reverse-engineered both theprimary key and the _NSAKEY into PGP-compatible format and published themto the key servers. [cite web |title=The reverse-engineered keys |publisher=Cypherspace |date=1999-09-06 |url=http://cypherspace.org/adam/hacks/ms-nsa-key.html |accessdate=2007-01-07]Microsoft's Primary (_KEY variable) CAPI Signature Key
Type Bits/KeyID Date User ID pub 1024/346B5095 1999/09/06 Microsoft's CAPI key=ms8C -----END PGP PUBLIC KEY BLOCK-----
Microsoft's Secondary (_NSAKEY variable, now _KEY2) CAPI Signature Key
Type Bits/KeyID Date User ID pub 1024/51682D1F 1999/09/06 NSA's Microsoft CAPI key
ee also
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Trusted Computer System Evaluation Criteria References
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