Nacre**Nacre, or mother-of-pearl, is one of nature's remarkable examples of a durable and break-resistant structure.: Durable, Secure and Energy-Efficient Non-Volatile Memory Utilizing Data Versioning

As we begin to utilize non-volatile memory (NVM) technologies as main memory elements, new challenges will emerge. While non-volatility is a desirable feature to save energy, it creates security vulnerabilities since data will persistent after system power-off. Data stored in NVMs can be secured using data encryption. However, side effects imposed by memory encryption result in excessive bit writes, which will drastically reduce NVM lifetimes and increase energy consumption. In this paper, we propose Nacre to bridge the gap between fully encrypted and unencrypted NVMs. Nacre exploits standard counter-mode encryption to maintain security. By tracking the different versions of the modified data in each memory writeback, Nacre attempts to limit the number of bit writes. Selective re-encryption is performed based on the history of the modified data in cache lines. We show that on average, Nacre improves memory lifetime by 53 percent (2.87x) as compared to state-of-the-art (full encryption) schemes. In addition, Nacre only increases energy consumption by 6 percent versus an unencrypted memory system.