PCM is a popular backing memory for DRAM main memory in tiered memory systems. PCM has asymmetric access energy; writes dominate reads. MLC asymmetry can vary by an order of magnitude. Many schemes have been developed to take advantage of the asymmetric patterns of 0s and 1s in the data to reduce write energy. Because the memory is non-volatile, data can be recovered via physical attack or across system reboot cycles. To protect information stored in PCM against these attacks requires encryption. Unfortunately, most encryption algorithms scramble 0s and 1s in the data, effectively removing any patterns and negatively impacting schemes that leverage data bias and similarity to reduce write energy. In this paper, we introduce Virtual Coset Coding (VCC) as a workload-independent approach that reduces costly symbol transitions for storing encrypted data. VCC is based on two ideas. First, using coset encoding with random coset candidates, it is possible to effectively reduce the frequency of costly bit/symbol transitions when writing encrypted data. Second, a small set of random substrings can be used to achieve the same encoding efficiency as a large number of random coset candidates, but at a much lower encoding/decoding cost. Additionally, we demonstrate how VCC can be leveraged for energy reduction in combination with fault-mitigation and fault-tolerance to dramatically increase the lifetimes of endurance-limited NVMs, such as PCM. We evaluate the design of VCC and demonstrate that it can be implemented on-chip with only a nominal area overhead. VCC reduces dynamic energy by 22-28% while maintaining the same performance. Using our multi-objective optimization approach achieves at least a 36% improvement in lifetime over the state-of-the-art and at least a 50% improvement in lifetime vs. an unencoded memory, while maintaining its energy savings and system performance.

翻译：PCM 是一种在分层内存系统中对 DRAM 主记忆的流行支持记忆。 PCM 拥有不对称的存取能量; 写主写主写主写。 刚果解放运动的不对称性能可能因数量不同而变化。 许多计划已经开发出来,以利用数据中0和1的不对称模式来减少写写能量。 由于记忆不易挥发, 数据可以通过实物攻击或系统重启动周期来恢复。 保护 PCM 中储存的这些攻击的信息需要加密。 不幸的是, 大多数加密算法在数据中拼凑0和1个, 有效地消除任何模式, 并产生负面影响, 利用数据偏差和类似功能来减少写作能量。 在本文件中, 我们采用虚拟 Cose Cose 编码(VCC ) 是一种依赖工作量不固定的模式, 减少存储加密数据的成本。 首先, 与随机的 VCC 候选人进行调试算, 只能有效地降低 VCB- symolt 的能量转换频率。 其次, 使用少量随机的子串拼算方法可以降低 VCM 效率, 而我们用一个随机的内存的节算方法来降低成本设计。