An apparatus including a BIOS read only memory (ROM) and a tamper detector. The BIOS ROM includes BIOS contents stored as plaintext, and an encrypted message digest comprising an encrypted version of a first message digest that corresponds to the BIOS contents. The tamper detector is coupled to the BIOS ROM, and accesses the BIOS contents and the encrypted message digest upon reset of a microprocessor, and directs the microprocessor to generate a second message digest corresponding to the BIOS contents and a decrypted message digest corresponding to the encrypted message digest using the same algorithms and key that were employed to generate the first message digest and the encrypted message digest, and compares the second message digest with the decrypted message digest, and precludes the operation of the microprocessor if the second message digest and the decrypted message digest are not equal.