Imbalance-Aware Scheduler for Fast and Secure Ring ORAM Data Retrieval

Data encryption can enhance data privacy but can not prevent privacy leakage completely. Side channels such as memory access pattern can also leak critical information in the program, while encryption cannot help when the access addresses are exposed to the attackers. Oblivious RAM (ORAM) was proposed to eliminate the access pattern leakage, and it can be incorporated with the memory controller to obfuscate and reshuffle memory accesses. Tree-based ORAM, such as Path ORAM and Ring ORAM, is a cost-effective ORAM organization, and it obfuscates the memory access pattern by reading and remapping data blocks along the path. Ring ORAM can achieve a better online data retrieval performance with a read protocol which only reads selective blocks along the path, compared to Path ORAM. However, the read path operation in Ring ORAM does not take the implementation of multi-channel memory system into consideration, which yields a potential bandwidth waste and a slower response time. Therefore, in this work, we investigate the root cause of the bandwidth waste and propose a fast and secure scheduler which balances the read path operation for Ring ORAM. Our scheduling schemes can improve the read operation response time as well as the overall system performance. The experimental results show that the read path latency for data retrieval can be reduced by 33% compared to the baseline Ring ORAM implementation.