LEO: Low Overhead Encryption ORAM for Non-Volatile Memories

Abstract

Data confidentiality attacks utilizing memory access patterns threaten exposure of data in modern main memories. Oblivious RAM (ORAM) is an effective cryptographic primitive developed to thwart access-pattern-based attacks in DRAM-based systems. However, in emerging non-volatile memory (NVM) systems, the increased writes due to encryption of multiple data blocks on every Path ORAM (state-of-the-art efficient ORAM) access impose significant energy, lifetime, and performance overheads. LEO ( L ow overhead E ncryption O RAM ) is an efficient Path ORAM encryption architecture that addresses the high write overheads of ORAM integration in NVMs, while providing security equivalent to the baseline Path ORAM. LEO reduces NVM cell writes by securely decreasing the number of block encryptions during the write phase of a Path ORAM access. LEO uses a secure, two-level counter mode encryption framework that opportunistically eliminates re-encryption of unmodified blocks, reducing NVM writes. Our evaluations show that on average, LEO decreases NVM energy by 60 percent, improves lifetime by 1.51 $\times$ , and increases performance by 9 percent over the baseline Path ORAM.