Use of hashing in a secure boot loader

摘要

Machine instructions comprising a bootstrap code are buried within a critical component of an electronic game console where they cannot readily be accessed or modified. A preloader portion in a read only memory (ROM) is hashed by the bootstrap code and the result is compared to an expected hash value maintained in the bootstrap code. Further verification of the boot-up process is carried out by the preloader, which hashes the code in ROM to obtain a hash value for the code. The result is verified against a digital signature value that defines an expected value for this hash. Failure to obtain any expected result terminates the boot-up process. Since the bootstrap code confirms the preloader, and the preloader confirms the remainder of the code in ROM, this technique is useful for ensuring that the code used for booting up the device has not been modified or replaced.