Secure Cryptoprocessor - Degree of Security

Degree of Security

Secure cryptoprocessors, while useful, are not invulnerable to attack, particularly for well-equipped and determined opponents (e.g. a government intelligence agency) who are willing to expend massive resources on the project.

One attack on a secure cryptoprocessor targeted the IBM 4758. A team at the University of Cambridge reported the successful extraction of secret information from an IBM 4758, using a combination of mathematics, and special-purpose codebreaking hardware.

While the vulnerability they exploited was a flaw in the software loaded on the 4758, and not the architecture of the 4758 itself, their attack serves as a reminder that a security system is only as secure as its weakest link: the strong link of the 4758 hardware was rendered useless by flaws in the design and specification of the software loaded on it.

Smartcards are significantly more vulnerable, as they are more open to physical attack.

In the case of full disk encryption applications, especially when implemented without a boot PIN, a cryptoprocessor would not be secure against a cold boot attack if data remanence could be exploited to dump memory contents after the operating system has retrieved the cryptographic keys from its TPM.

Some secure cryptoprocessors contain dual processor cores and generate inaccessible encryption keys when needed so that even if the circuitry is reverse engineered, it will not reveal any keys that are necessary to securely decrypt software booted from encrypted flash memory or communicated between cores.

The first single-chip cryptoprocessor design was for copy protection of personal computer software (see US Patent 4,168,396, Sept 18, 1979) and was inspired by Bill Gates' Open Letter to Hobbyists.