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Unveiling your keystrokes: A Cache-based Side-channel Attack on Graphics Libraries

Operating systems use shared memory to improve performance. However, as shown in recent studies, attackers can exploit CPU cache side-channels associated with shared memory to extract sensitive information. The attacks that were previously attempted typically only detect the presence of a certain operation and require significant manual analysis to identify and evaluate their effectiveness. Moreover, very few of them target graphics libraries which are commonly used, but difficult to attack. In this paper, we consider the execution time of shared libraries as the side-channel, and showcase a completely automated technique to discover and select exploitable side-channels on shared graphics libraries. In essence, we first collect the cache lines accessed by a victim process during different key presses offline, and then use machine learning to infer the best cache lines (e.g., easily measurable, robust to noise, high information leakage) for a flush and reload attack. We are able to discover effective strategies to classify what keys have been pressed. Using this approach, we not only preclude the need for manual analyses of code and traces — the automated system discovered many previously unknown sidechannels of the type we are interested in, but also achieve high precision in terms of inferring the sensitive information entered on desktop and Android platforms. We show that our approach infers the passwords with lowercase letters and numbers 10,000 1,000,000 times faster than random guessing. For a large fraction of PINs consisting of 4 to 6 digits, we are able to infer them within 20 and 80 guesses respectively. Finally, we suggest ways to mitigate these attacks.