UBC Theses and Dissertations

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UBC Theses and Dissertations

Lightweight mitigation against transient cache side-channel attacks He, Muchen


Today, nearly all modern devices, including smartphones, PCs, and cloud servers, benefit significantly from two architectural advancements that speed up computation. First, speculative execution allows the execution of instructions ahead of time; and second, cache memory store data close to the processor to reduce latency of memory operations. Unfortunately, these features also make compute systems vulnerable to security holes known as transient side-channel attacks. These attacks exploit predictive mechanisms and use mis-speculated instructions to modify the cache persistently as a side channel. Such attacks enables leakage of private data, such as cryptographic keys. Full-fledged mitigations against transient attacks have come at a significant performance cost. They either try to stop potential leakage at the source — where it is speculatively execution instructions — and penalize many “innocent” executions or laboriously restore past states in the memory hierarchy. This research focuses on mitigating the transient side-channel attacks while minimizing performance loss. Our approach combines significantly more efficient protection schemes inside the cache hardware, the destination, to stop potential leaks. We identify and leverage a specific memory access pattern to detect an ongoing cache side-channel attack and localize the protection to where it occurs. We propose FantôMiss, our mitigation strategy that allows cache state changes speculatively but also tracks the modified cache lines under speculation. Then, for subsequent accesses to those speculated cache lines, we generate fake cache misses that traverse the memory hierarchy that conceals speculative cache states, thereby closing the side-channel. Crucially, the increased latency is not imposed upon all load instructions but only on loads that read potential leak sources. As a result, FantôMiss significantly outperforms prior proposed mitigations, with execution-time overheads of just 0.5% and 1.6%(geometric-mean) across the PARSEC and SPEC benchmark suites.

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