Sharing is Caring-On the Protection of Arithmetic Logic Units against Passive Physical Attacks

摘要

Embedded systems are often used in security-critical scenarios where physical access of an adversary cannot be prevented. An attacker with unrestricted physical access to an embedded device could thus use observation-based attacks like power analysis or chip probing techniques to extract chip-internal secrets. In this work, we investigate how to counteract first-order passive physical attacks on an embedded microcontroller. In particular, we focus on the protection of the central point of data processing in the microcontroller design-the arithmetic logic unit (ALU)-with the provably secure threshold implementation (TI) masking scheme. Our results show that the amount of required fresh random bits-a problem many masked implementations suffer from-can be reduced to only one bit per ALU access and clock cycle. The total chip area overhead for implementing the whole microcontroller of our case study as a three-share TI is about a factor of 2.8.