Active attestation of embedded systems
An active attestation apparatus verifies at runtime the integrity of untrusted machine code of an embedded system residing in a memory device while it is being run/used with while slowing the processing time less than other methods. The apparatus uses an integrated circuit chip containing a microcontroller and a reprogrammable logic device, such as a field programmable gate array (FPGA), to implement software attestation at runtime and in less time than is typically possible with comparable attestation approaches, while not requiring any halt of the processor in the microcontroller. The reprogrammable logic device includes functionality to load an encrypted version of its configuration and operating code, perform a checksum computation, and communicate with a verifier. The checksum algorithm is preferably time optimized to execute computations in the reprogrammable logic device in the minimum possible time.
1. An active attestation apparatus for verifying the integrity of untrusted machine code, the runtime attestation apparatus comprising:
a reprogrammable logic device disposed on an integrated circuit chip, wherein the reprogrammable logic device is configured by a processor preloader that is downloaded to the reprogrammable logic device via a trusted bitstream; and
a processor disposed on the integrated circuit chip with the reprogrammable logic device, wherein the processor downloads the processor preloader from the reprogrammable logic device, is booted by the processor preloader to a trusted state, downloads the untrusted machine code from memory locations of a memory device, and executes the untrusted machine code,
wherein, as the processor executes the untrusted machine code, the reprogrammable logic device executes an attestation algorithm over the memory locations of the memory device from which the processor downloaded the untrusted machine code.
2. The active attestation apparatus of claim 1 wherein the reprogrammable logic device comprises a field-programmable gate array.
3. The active attestation apparatus of claim 1 wherein the processor comprises an Advanced Reduced Instruction Set Computer (RISC).