PS-ORAM: efficient crash consistency support for oblivious RAM on NVM

Oblivious RAM (ORAM) is a provable secure primitive to prevent access pattern leakage on the memory bus. By randomly remapping the data blocks and accessing redundant blocks, ORAM prevents access pattern leakage through ob-fuscation. Byte-addressable non-volatile memory (NVM) is considered as the candidate for main memory due to its better scalability, competitive performance, and persistent data store. While there is much prior work focusing on improving ORAM's performance on the conventional DRAM-based memory system, when the memory technology shifts to use NVM, ensuring an efficient crash-consistent ORAM is needed for security, correctness, and performance. Directly using traditional software-based crash consistency support for ORAM system is not only expensive but also insecure. In this work, we study how to persist ORAM construction with an NVM-based memory system. To support crash consistency without damaging ORAM system security and compromising the performance, we propose PS-ORAM. PS-ORAM consists of a novel ORAM controller design and a set of ORAM access protocols that support crash consistency. We evaluate PS-ORAM with the system without crash consistency support, non-recursive and recursive PS-ORAM only incurs 4.29% and 3.65% additional performance overhead. The results show that PS-ORAM not only supports effective crash consistency with minimal performance and hardware overhead but also is friendly to NVM lifetime.