@article{han_tuck_awad_2023, title={Thoth: Bridging the Gap Between Persistently Secure Memories and Memory Interfaces of Emerging NVMs}, ISSN={["1530-0897"]}, DOI={10.1109/HPCA56546.2023.10070991}, abstractNote={Emerging non-volatile memories (NVMs) are expected to be part of future computing systems, including cloud systems and edge devices. In addition to the high density (and hence large capacities) NVMs can provide, they feature ultra-low idle power which makes them very promising for edge computing and data centers. Additionally, NVMs’ ability to retain data upon system crash (e.g., power outage or software bug) makes them a great candidate for high-availability and persistent applications. However, NVMs’ data retention capability brings in security challenges and further complicates today’s secure memory implementations; to ensure correct and secure system recovery, the data and security metadata must be persisted atomically (i.e., up-to-date in memory upon a crash).Despite the many efforts for rethinking secure memory implementations to enable crash-consistency, we observe that the state-of-the-art solutions are based on a major assumption that may not be suitable for future memory interfaces. Specifically, the majority of today’s solutions assume that either the encryption counter and/or message-authentication code (MAC) can be co-located with data by directly or indirectly leveraging the otherwise Error-Correcting Codes (ECC) bits. However, we observe that emerging interfaces and standards delegate the ECC calculation and management to happen inside the memory module, which makes it possible to remove extra bits for ECC in memory interfaces. Thus, all today’s solutions may need to separately persist the encrypted data, its MAC, and its encryption counter upon each memory write. To mitigate this issue, we propose a novel solution, Thoth, which leverages a novel off-chip persistent partial updates combine buffer that can ensure crash consistency at the cost of a fraction of the write amplification by the state-of-the-art solutions when adapted to future interfaces. Based on our evaluation, Thoth improves the performance by an average of 1.22x (up to 1.44x) while reducing write traffic by an average of 32% (up to 40%) compared to the baseline Anubis when adapted to future interfaces.}, journal={2023 IEEE INTERNATIONAL SYMPOSIUM ON HIGH-PERFORMANCE COMPUTER ARCHITECTURE, HPCA}, author={Han, Xijing and Tuck, James and Awad, Amro}, year={2023}, pages={94–107} }
 @article{han_tuck_awad_2022, title={Horus: Persistent Security for Extended Persistence-Domain Memory Systems}, ISSN={["1072-4451"]}, DOI={10.1109/MICRO56248.2022.00087}, abstractNote={Persistent memory presents a great opportunity for crash-consistent computing in large-scale computing systems. The ability to recover data upon power outage or crash events can significantly improve the availability of large-scale systems, while improving the performance of persistent data applications (e.g., database applications). However, persistent memory suffers from high write latency and requires specific programming model (e.g., Intel’s PMDK) to guarantee crash consistency, which results in long latency to persist data. To mitigate these problems, recent standards advocate for sufficient back-up power that can flush the whole cache hierarchy to the persistent memory upon detection of an outage, i.e., extending the persistence domain to include the cache hierarchy. In the secure NVM with extended persistent domain(EPD), in addition to flushing the cache hierarchy, extra actions need to be taken to protect the flushed cache data. These extra actions of secure operation could cause significant burden on energy costs and battery size. We demonstrate that naive implementations could lead to significantly expanding the required power holdup budget (e.g., 10.3x more operations than EPD system without secure memory support). The significant overhead is caused by memory accesses of secure metadata. In this paper, we present Horus, a novel EPD-aware secure memory implementation. Horus reduces the overhead during draining period of EPD system by reducing memory accesses of secure metadata. Experiment result shows that Horus reduces the draining time by 5x, compared with the naive baseline design.}, journal={2022 55TH ANNUAL IEEE/ACM INTERNATIONAL SYMPOSIUM ON MICROARCHITECTURE (MICRO)}, author={Han, Xijing and Tuck, James and Awad, Amro}, year={2022}, pages={1255–1269} }