GPU Obfuscation: Attack and Defense Strategies

Conventional attacks against existing logic obfuscation techniques rely on the presence of an activated hardware for analysis. In reality, obtaining such activated chips may not always be practical, especially if the on-chip test structures are disabled. In this paper, we develop an iterative SAT formulation based attack strategy for deobfuscating many-core GPU hardware without any requirement of an activated chip. Our experiments on a real testbed using NVIDIA's SASSIFI framework reveal that more than 95% of the application runs on such an approximately unlocked GPU result in correct outcomes with 95% confidence-level and 5% confidence-interval. To counter the proposed attack, we develop a Cache Locking countermeasure which significantly degrades the performance of GPGPU applications for a wrong cache-key.