SECURE BIOS MECHANISM IN A TRUSTED COMPUTING SYSTEM

摘要

An apparatus including a ROM and a microprocessor. The ROM includes BIOS contents that are stored as plaintext and an encrypted digest. The encrypted digest includes an encrypted version of a first digest corresponding to the BIOS contents. The microprocessor is coupled to the BIOS ROM, and includes a tamper timer and a tamper detector. The tamper timer periodically generates an interrupt at a prescribed interval. The tamper detector accesses the BIOS contents and the encrypted digest upon assertion of the interrupt, and directs the microprocessor to generate a second digest corresponding to the BIOS contents and a decrypted digest corresponding to the encrypted digest using the same algorithms and key that were employed to generate the first digest and the encrypted digest, and compares the second digest with the decrypted digest, and precludes operation of the microprocessor if the second digest and the decrypted digest are not equal.

主权项

1. An apparatus for protecting a basic input/output system (BIOS) in a computing system, the apparatus comprising:
a BIOS read only memory (ROM), comprising:
BIOS contents, wherein said BIOS contents are stored as plaintext; andan encrypted message digest, wherein said encrypted message digest comprises an encrypted version of a first message digest that corresponds to said BIOS contents; a tamper timer, configured to periodically generate a BIOS check interrupt that interrupts normal operation of the computing system at a prescribed interval; and a tamper detector, operatively coupled to said BIOS ROM and said tamper timer, configured to access said BIOS contents and said encrypted message digest upon assertion of said BIOS check interrupt, and configured to direct a microprocessor to generate a second message digest corresponding to said BIOS contents and a decrypted message digest corresponding to said encrypted message digest using the same algorithms and key that were employed to generate said first message digest and said encrypted message digest, and configured to compare said second message digest with said decrypted message digest, and configured to preclude said operation of said microprocessor if said second message digest and said decrypted message digest are not equal.