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    计数器溢出可感知的非易失性存储器安全重加密延迟优化技术

    Counter Overflow-Aware Optimization Technique for Secure Re-Encryption Delay in Non-Volatile Memory

    • 摘要: 非易失性存储器(Non-Volatile Memory,NVM)因其断电后数据持久保存、高密度和大容量的优势,已经成为学术界与工业界的研究热点.然而,这种持久性特性也使NVM更容易遭受未经授权访问和数据篡改等安全威胁。为此,研究人员提出一系列安全机制,以保障NVM在存储和访问过程中的数据机密性和完整性。通常,安全的 NVM 系统采用加密和完整性验证技术,但直接对 NVM 进行加密会引发写放大问题,进而导致写入延迟增加和能耗上升等性能瓶颈.为了解决这一问题,本文提出了一种计数器溢出可感知的非易失性存储器安全重加密延迟优化技术(ERED),其包含 W-ERED 和 L-ERED 两种技术。数据行的重加密频率通常由更新最频繁的字决定,W-ERED通过为局部计数器设置标志位,精准识别频繁溢出的字。当局部计数器溢出时,仅对溢出的字使用新的行计数器加密,而对未溢出的字仍然使用旧的行计数器进行加密,从而避免了不必要的重加密。在此基础上,L-ERED方案考虑到数据页的重加密速度主要受页内溢出频率最高的数据行影响,通过为行计数器设置溢出标志,确保在溢出发生时,仅对溢出的数据行使用主计数器进行重加密,显著减少了由于“行计数器溢出”而需要重加密的数据块粒度。另外,为了进一步优化写入开销并增强系统的崩溃恢复能力,本文提出改进方案STAR+.引入计数器写入过滤机制,仅当缓存中计数器更新达到预设阈值时才写入NVM,从而减少写入操作。在崩溃恢复过程中,STAR+依赖Osiris技术,通过影子计数器记录增量更新,恢复时读取持久化计数器值,应用日志增量并验证其正确性,重建计数器状态。此外,STAR+通过更新叶子节点和父节点的MAC值,递归计算上层哈希值,从而恢复完整性树,确保数据和元数据的一致性。实验结果表明,ERED系列方案在加密开销优化上成果显著:与 SECRET相比,W-ERED在平均位翻转次数上降低了5%,写入延迟降低了 11%,写入能耗降低了 6%,而存储开销仅增加了8/512。在 L-ERED 方案中,重新加密的行数量仅为 BASE 方案的 26.7% 和 RSR 方案的 47.7%,且仅需要增加1/512的存储开销,显著减少了行计数器溢出时的重新加密开销。此外,在崩溃一致性保障方面,STAR+方案较其前身STAR技术展现出更优性能:NVM写入次数减少9.8%,性能开销降低3.1%,且恢复时间与STAR方案几乎持平。

       

      Abstract: Non-Volatile Memory (NVM), with its advantages of data persistence after power loss, high density, and large capacity, has become a significant focus of research in both academia and industry. However, this persistence characteristic also makes NVM more susceptible to security threats such as unauthorized access and data tampering. To address this, researchers have proposed a series of security mechanisms to ensure data confidentiality and integrity during NVM storage and access. Typically, secure NVM systems employ encryption and integrity verification techniques. However, direct encryption of NVM can lead to write amplification issues, resulting in performance bottlenecks such as increased write latency and energy consumption. To tackle this issue, this paper proposes a Counter Overflow-Aware Non-Volatile Memory Secure Re-encryption Delay optimization technique (ERED), which includes two schemes: W-ERED and L-ERED. The re-encryption frequency of a data line is often determined by its most frequently updated word. W-ERED accurately identifies frequently overflowing words by setting flag bits for local counters. When a local counter overflows, only the overflowing word is encrypted using a new line counter, while non-overflowing words are still encrypted with the old line counter, thereby avoiding unnecessary re-encryptions. Building upon this, the L-ERED scheme considers that the re-encryption speed of a data page is primarily affected by the data line with the highest overflow frequency within that page. By setting overflow flags for line counters, L-ERED ensures that only overflowing data lines are re-encrypted using the main counter upon overflow, significantly reducing the granularity of data blocks requiring re-encryption due to "line counter overflow." Furthermore, to further optimize write overhead and enhance system crash recovery capabilities, this paper proposes an improved scheme, STAR+. STAR+ introduces a counter write filtering mechanism, where counters are written to NVM only when their updates in the cache reach a preset threshold, thereby reducing write operations. During crash recovery, STAR+ leverages the Osiris technique, employing shadow counters to record incremental updates. For recovery, it reads persisted counter values, applies logged increments, verifies their correctness, and reconstructs the counter state. Additionally, STAR+ restores the integrity tree by updating the MAC values of leaf and parent nodes and recursively calculating upper-level hash values, ensuring data and metadata consistency. Experimental results demonstrate that the ERED series of schemes achieve significant improvements in encryption overhead optimization: compared to SECRET, W-ERED reduces average bit flips by 5%, write latency by 11%, and write energy by 6%, with only an 8/512 increase in storage overhead. In the L-ERED scheme, the number of re-encrypted lines is only 26.7% of that in the BASE scheme and 47.7% of that in the RSR scheme, requiring only an additional 1/512 storage overhead, thereby significantly reducing the re-encryption overhead during line counter overflows. Moreover, regarding crash consistency assurance, STAR+ demonstrates superior performance compared to its predecessor, STAR, with 9.8% fewer NVM writes, a 3.1% reduction in performance overhead, and recovery time comparable to STAR.

       

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