CacheTree: Reducing Integrity Verification Overhead of Secure Nonvolatile Memories

Emerging nonvolatile memories (NVMs), while exhibiting great potential to be DRAM alternatives, are vulnerable to security attacks. Secure NVM designs demand data persistence on top of traditional confidentiality and integrity protection. A simple adaption of existing secure memory designs would incur non-negligible overheads, including performance degradation, NVM lifetime reduction, and energy consumption increase. In this article, we propose CacheTree to address the integrity verification overhead for secure NVMs. By constructing extra Merkle trees (MTs) on top of metadata cache, CacheTree helps to authenticate the volatile cache contents, which enables the adoption of write-back policy and prevents frequent NVM writes in persisting metadata. We then adopt CacheTree to address the integrity verification in secure NVM, in particular, the overheads in persisting message authentication codes (for protecting the integrity of user data at memory line level) and persisting the main MT (for protecting the integrity of the whole memory space). Our experimental results show that CacheTree, with less than 0.5% storage overhead, achieves up to 20.1% performance improvement, 44.3% lifetime increase, and 43.7% energy consumption reduction over the state-of-the-art solutions.