Chunked-Cache: On-Demand and Scalable Cache Isolation for Security Architectures

TL;DR

Chunked-Cache offers a flexible, on-demand cache partitioning solution for TEE architectures that enhances security against side-channel attacks without performance penalties.

Contribution

It introduces a novel set-associative cache design enabling dynamic, fine-grained cache partitioning for security, outperforming traditional methods in scalability and efficiency.

Findings

Provides side-channel-resilient cache for sensitive code

Achieves 43% better performance than conventional partitioning

Supports more protection domains with better scalability

Abstract

Shared cache resources in multi-core processors are vulnerable to cache side-channel attacks. Recently proposed defenses have their own caveats: Randomization-based defenses are vulnerable to the evolving attack algorithms besides relying on weak cryptographic primitives, because they do not fundamentally address the root cause for cache side-channel attacks. Cache partitioning defenses, on the other hand, provide the strict resource partitioning and effectively block all side-channel threats. However, they usually rely on way-based partitioning which is not fine-grained and cannot scale to support a larger number of protection domains, e.g., in trusted execution environment (TEE) security architectures, besides degrading performance and often resulting in cache underutilization. To overcome the shortcomings of both approaches, we present a novel and flexible set-associative cache partitioning design for TEE architectures, called Chunked-Cache. Chunked-Cache enables an execution context to "carve" out an exclusive configurable chunk of the cache if the execution requires side-channel resilience. If side-channel resilience is not required, mainstream cache resources are freely utilized. Hence, our solution addresses the security-performance trade-off practically by enabling selective and on-demand utilization of side-channel-resilient caches, while providing well-grounded future-proof security guarantees. We show that Chunked-Cache provides side-channel-resilient cache utilization for sensitive code execution, with small hardware overhead, while incurring no performance overhead on the OS. We also show that it outperforms conventional way-based cache partitioning by 43%, while scaling significantly better to support a larger number of protection domains.