MORE2: Morphable Encryption and Encoding for Secure NVM

Abstract

Memory encryption can enhance the security of Non-volatile memories (NVMs), but it significantly increases the data bits written to NVMs and leads to severe lifetime and performance degradation. Current encryption techniques aim to reduce the re-encryption to many existing clean words, which unfortunately suffer from high encryption overheads (i.e. latency and energy) and many unnecessary writes. In the meantime, compression techniques can reduce the writes of encrypted NVM. However, we find that they may destroy the data patterns and increase the modified words, resulting in many encryptions in secure NVM. In this paper, we propose the MORphable Encryption and Encoding (MORE <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) scheme to address these problems. Our MORphable Encryption (MORE) technique aims to reduce the full-line re-encryption and avoid clean line encryption. Besides, MORE proposes a prediction-based write scheme to avoid the encryption of clean lines, and pre-encrypt the lines that are predicted as dirty. Therefore, MORE can remove the encryption from the critical path of NVM. Furthermore, MORE <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> proposes the Morphable Selective Encoding (MSE) scheme to compress the modified words while preserving clean words. MORE <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> encrypts all metadata with the line counter to guarantee high security. Experimental results show that MORE <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> reduces the bit flips of encrypted NVM by 53.5 %, decreases the access latency by 27.32%, improves the IPC performance by 12.1 %, and reduces the write energy by 29.1 % compared with the state-of-the-art design.