ClepsydraCache -- Preventing Cache Attacks with Time-Based Evictions


Jan Philipp Thoma, Ruhr University Bochum; Christian Niesler, University of Duisburg-Essen; Dominic Funke, Gregor Leander, Pierre Mayr, and Nils Pohl, Ruhr University Bochum; Lucas Davi, University of Duisburg-Essen; Tim Güneysu, Ruhr University Bochum & DFKI


In the recent past, we have witnessed the shift towards attacks on the microarchitectural CPU level. In particular, cache side-channels play a predominant role as they allow an attacker to exfiltrate secret information by exploiting the CPU microarchitecture. These subtle attacks exploit the architectural visibility of conflicting cache addresses. In this paper, we present ClepsydraCache, which mitigates state-of-the-art cache attacks using a novel combination of cache decay and index randomization. Each cache entry is linked with a Time-To-Live (TTL) value. We propose a new dynamic scheduling mechanism of the TTL which plays a fundamental role in preventing those attacks while maintaining performance. ClepsydraCache efficiently protects against the latest cache attacks such as Prime+(Prune+)Probe. We present a full prototype in gem5 and lay out a proof-of-concept hardware design of the TTL mechanism, which demonstrates the feasibility of deploying ClepsydraCache in real-world systems.

Open Access Media

USENIX is committed to Open Access to the research presented at our events. Papers and proceedings are freely available to everyone once the event begins. Any video, audio, and/or slides that are posted after the event are also free and open to everyone. Support USENIX and our commitment to Open Access.

@inproceedings {285381,
author = {Jan Philipp Thoma and Christian Niesler and Dominic Funke and Gregor Leander and Pierre Mayr and Nils Pohl and Lucas Davi and Tim G{\"u}neysu},
title = {{ClepsydraCache} -- Preventing Cache Attacks with {Time-Based} Evictions},
booktitle = {32nd USENIX Security Symposium (USENIX Security 23)},
year = {2023},
isbn = {978-1-939133-37-3},
address = {Anaheim, CA},
pages = {1991--2008},
url = {},
publisher = {USENIX Association},
month = aug

Presentation Video