EVALUATING THE USE OF BOOT IMAGE ENCRYPTION ON THE TALOS II ARCHITECTURE

Abstract

Critical infrastructure devices operating in unprotected end-node environments are vulnerable to malicious actors who conduct hardware attacks such as reverse engineering and side-channel analysis. Boot data is rarely encrypted and typically travels across an accessible bus, enabling the data to be easily intercepted during system start-up. Encrypting the firmware would make reverse engineering extremely difficult for malicious actors and competitors. It would improve the effectiveness of tamper detection methods and deter zero-day vulnerability discovery. Increasing boot security could be a fundamental part of decreasing attack surfaces across the critical infrastructure sectors.

This chapter describes a Talos II architecture implementation that encrypts a section of the boot image and decrypts it during initial program load. During power-on, the encrypted image travels across the Low Pin Count bus into a POWER9 module Level 3 cache and is decrypted in the processor. Boot image encryption is implemented using ciphers of different strengths. An analysis of their efficiency is conducted to determine the optimal algorithm.