A Memory Hierarchy Protected against Side-Channel Attacks

In the vulnerability analysis of System on Chips, memory hierarchy is considered among the most valuable element to protect against information theft. Many first-order side-channel attacks have been reported on all its components from the main memory to the CPU registers. In this context, memory hierarchy encryption is widely used to ensure data confidentiality. Yet, this solution suffers from both memory and area overhead along with performance losses (timing delays), which is especially critical for cache memories that already occupy a large part of the spatial footprint of a processor. In this paper, we propose a secure and lightweight scheme to ensure the data confidentiality through the whole memory hierarchy. This is done by masking the data in cache memories with a lightweight mask generator that provides masks at each clock cycle without having to store them. Only 8-bit Initialization Vectors are stored for each mask value to enable further recomputation of the masks. The overall security of the masking scheme is assessed through a mutual information estimation that helped evaluate the minimum number of attack traces needed to succeed a profiling side-channel attack to 592 K traces in the attacking phase, which provides an acceptable security level in an analysis where an example of Signal to Noise Ratio of 0.02 is taken. The lightweight aspect of the generator has been confirmed by a hardware implementation that led to resource utilization of 400 LUTs