EHAP-ORAM：高效的硬件辅助持久性非易失性存储器ORAM系统
EHAP-ORAM: Efficient Hardware-Assisted Persistent ORAM System for Non-volatile Memory
摘要：
不经意RAM（ORAM）是一种可证明安全的原语，用于防止存储器总线上的访问模式泄漏。它作为可信片上组件和不可信外部存储器系统之间的中间层，将原始存储器访问模式调制成不可区分的存储器序列。通过随机重新映射数据块和访问冗余块，ORAM通过混淆防止访问模式泄漏。虽然有许多先前的工作集中在提高传统的基于DRAM的存储器系统上的ORAM的性能，但当存储器技术转向使用非易失性存储器（NVM）时，关于如何有效地支持ORAM的崩溃一致性的新挑战出现。在这项工作中，我们提出了EHAP-ORAM，研究如何持久化ORAM建设与基于NVM的内存系统。我们首先分析了持久化ORAM系统的设计需求，并讨论了为数据和ORAM元数据保持崩溃一致性和原子性的必要性。接下来，我们将讨论持久ORAM系统设计中的一些挑战，并针对这些挑战提出一些解决方案。然后，我们提出了改进的片上ORAM控制器架构。在改进片上ORAM控制器硬件架构的基础上，提出了不同的持久化协议，以保证ORAM系统的崩溃一致性，并满足PosMap元数据在可信/不可信片外NVM中持久化时的安全性。所提出的架构和持久化协议的步骤，最大限度地减少了开销和泄漏过程中的写回。最后，我们比较了我们的持久ORAM与系统没有崩溃一致性支持，表明在非递归和递归的情况下，EHAP-ORAM只会带来3.36%和3.65%的性能开销。结果表明，EHAP-ORAM可以支持有效的崩溃一致性，最小的性能和硬件开销。
英文摘要：
Oblivious RAM (ORAM) is a provable secure primitive to prevent access pattern leakage on the memory bus. It serves as the intermediate layer between the trusted on-chip components and the untrusted external memory systems to modulate the original memory access patterns into indistinguishable memory sequences. By randomly remapping the data blocks and accessing redundant blocks, ORAM prevents access pattern leakage through obfuscation. 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 non-volatile memory (NVM), new challenges come up as to how to efficiently support crash consistency for ORAM. In this work, we propose EHAP-ORAM, which studies how to persist ORAM construction with an NVM-based memory system. We first analyze the design requirements for a persistent ORAM system and discuss the need to preserve crash consistency and atomicity for both data and ORAM metadata. Next, we discuss some of the challenges in the design of a persistent ORAM system and propose some solutions to those challenges. Then, we propose the modified on-chip ORAM controller architecture. Based on the improved hardware architecture of the ORAM controller on-chip, we propose different persistency protocols to ensure the crash consistency of the ORAM system and satisfy that the metadata in PosMap is safe when it is persisted to NVM in trusted/untrusted off-chip. The proposed architecture and persistency protocol steps minimize the overhead and leakage during the write-back process. Finally, we compared our persistent ORAM with the system without crash consistency support, show that in non-recursive and recursive cases, EHAP-ORAM only incurs 3.36% and 3.65% performance overhead. The results show that the EHAP-ORAM can support efficient crash consistency with minimal performance and hardware overhead.
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