PreSIT: Predict Cryptography Computations in SGX-Style Integrity Trees

In recent years, SGX-style integrity trees (SITs) have been applied in trusted execution environments (TEEs) to protect the off-chip memory security from physical attacks, replay attacks, etc. As a tradeoff, SIT implementations incur a huge performance overhead due to its extra computations and memory accesses. Recent works reduced the memory accesses and significantly increased the speed, but the performance overhead is still high. To tackle this challenge, this article performs an insight analysis under current SIT implementations, then identifies two critical remaining performance overhead causes: 1) hash and 2) decryption computations. Next, a novel design named PreSIT based on a proposed parallel operation flow is introduced. It performs prefetching and precomputes partial results of hash and decryption processes. By designing the prediction algorithm flow and predict-assisted algorithms, along with the proposed dedicated prediction data structure to effectively store and access the precomputed results, the performance overhead is further reduced. According to the evaluations of GEM5 on SPEC 2017, GAP, PARSEC, and SPLASH2x, PreSIT improves the average instruction per cycle (IPC) by 5.1% (at most 21.6%) based on the SIT in VAULT without any security degradation.