|
Microsoft, the NSA, and You, by Andrew Fernandes Microsoft Installs US Spy Agency with Windows Research Triangle Park, NC - 31 August 1999 - Between Hotmail hacks and browser bugs, Microsoft has a dismal track record in computer security. Most of us accept these minor security flaws and go on with life. But how is an IT manager to feel when they learn that in every copy of Windows sold, Microsoft may have installed a 'back door' for the National Security Agency (NSA - the USA's spy agency) making it orders of magnitude easier for the US government to access their computers? While investigating the security subsystems of WindowsNT4, Cryptonym's Chief Scientist Andrew Fernandes discovered exactly that - a back door for the NSA in every copy of Win95/98/NT4 and Windows2000. Building on the work of Nicko van Someren (NCipher), and Adi Shamir (the 'S' in 'RSA'), Andrew was investigating Microsoft's "CryptoAPI" architecture for security flaws. Since the CryptoAPI is the fundamental building block of cryptographic security in Windows, any flaw in it would open Windows to electronic attack. Normally, Windows components are stripped of identifying information. If the computer is calculating "number_of_hours = 24 * number_of_days", the only thing a human can understand is that the computer is multiplying "a = 24 * b". Without the symbols "number_of_hours" and "number_of_days", we may have no idea what 'a' and 'b' stand for, or even that they calculate units of time. In the CryptoAPI system, it was well known that Windows used special numbers called "cryptographic public keys" to verify the integrity of a CryptoAPI component before using that component's services. In other words, programmers already knew that windows performed the calculation "component_validity = crypto_verify(23479237498234...,crypto_component)", but no-one knew exactly what the cryptographic key "23479237498234..." meant semantically. Then came WindowsNT4's Service Pack 5. In this service release of software from Microsoft, the company crucially forgot to remove the symbolic information identifying the security components. It turns out that there are really two keys used by Windows; the first belongs to Microsoft, and it allows them to securely load CryptoAPI services; the second belongs to the NSA. That means that the NSA can also securely load CryptoAPI services... on your machine, and without your authorization. The result is that it is tremendously easier for the NSA to load unauthorized security services on all copies of Microsoft Windows, and once these security services are loaded, they can effectively compromise your entire operating system. For non-American IT managers relying on WinNT to operate highly secure data centers, this find is worrying. The US government is currently making it as difficult as possible for "strong" crypto to be used outside of the US; that they have also installed a cryptographic back-door in the world's most abundant operating system should send a strong message to foreign IT managers. There is good news among the bad, however. It turns out that there is a flaw in the way the "crypto_verify" function is implemented. Because of the way the crypto verification occurs, users can easily eliminate or replace the NSA key from the operating system without modifying any of Microsoft's original components. Since the NSA key is easily replaced, it means that non-US companies are free to install "strong" crypto services into Windows, without Microsoft's or the NSA's approval. Thus the NSA has effectively removed export control of "strong" crypto from Windows. A demonstration program that replaces the NSA key can be found on Cryptonym's website. Cryptonym: Bringing you the Next Generation of Internet Security, using cryptography, risk management, and public key infrastructure. Interview Contact: Andrew Fernandes Telephone: +1 919 469 4714 email: andrew@AT@cryptonym.com Fax: +1 919 469 8708 Cryptonym Corporation 1695 Lincolnshire Boulevard Mississauga, Ontario Canada L5E 2T2 http://www.cryptonym.com
|