PrefixWall: Mitigating Prefix Caching Side Channels in Shared LLM Systems
Large Language Models (LLMs) rely on optimizations like Automatic Prefix Caching (APC) to accelerate inference. APC works by reusing previously computed states for the beginning part of a request (prefix), when another request starts with the same text. While APC improves throughput, it introduces timing side channels: cache hits are faster than misses, creating observable latency differences. In multi-tenant systems, attackers can exploit these differences to infer sensitive information, e.g., by incrementally reconstructing another user's request by observing hit/miss patterns. Current defenses take a sledgehammer approach: they disable APC and cache sharing, isolating users, and sacrif...
| Authors | Panagiotis Georgios Pennas, Konstantinos Papaioannou, Marco Guarnieri et al. |
|---|---|
| Primary category | cs.CR |
| Published | 11 March 2026 |
| Last updated at source | 20 May 2026 |
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