TEE hardware improves fault tolerance only above two thirds
Breaking Fault Lines: Unifying TEE-Assisted BFT Consensus in Partially Trusted Worlds
Distributed, Parallel, and Cluster Computing
Summary
The paper studies how Trusted Execution Environments (TEEs), special secure hardware, can help improve agreement among computers even when some replicas are untrusted. The authors find that partial use of TEEs changes how many faulty nodes the system can handle, showing that fault tolerance only improves significantly when most nodes use TEEs. They design new methods and protocols that safely mix TEE and non-TEE nodes and speed up agreement steps using TEE-based guarantees. These protocols perform better than existing consensus methods, especially when only part of the system uses TEEs.
What this means in practice
- •For distributed system engineers: Build resilient consensus systems that integrate mixed hardware trust levels with faster agreement steps facilitated by trusted hardware nodes.
- •For cloud infrastructure teams: Deploy blockchain or distributed ledger services with partially trusted hardware environments ensuring both performance and fault tolerance.
Authors
Xiaoqing Wen, Tong Liu, Jianyu Niu, Jialin Li, Cong Wang, Yinqian Zhang, Chen Feng
Abstract
This paper revisits TEE-assisted BFT under a universal partial-TEE model, where an arbitrary subset of replicas execute inside TEEs while the remaining replicas operate without hardware trust guarantees. We show that heterogeneous trust changes the structure of quorum formation and fault tolerance. In particular, we derive a tight resilience bound f < max {n/3, m/2}, where n is the total number of replicas and m is the number of TEE-enabled replicas. The result reveals a sharp threshold phenomenon: TEEs improve fault tolerance only once they exceed two-thirds of the deployment. Guided by this characterization, we introduce two protocol principles: (1) a dual-quorum construction that safely combines TEE-only and mixed quorums, and (2) a TEE-leader fast path that leverages hardware-enforced non-equivocation to reduce both consensus and view-change latency. We realize these ideas in Raftel, which is, to our knowledge, the first HotStuff-style BFT protocol designed explicitly for arbitrary partial-TEE deployments, and in chained-Raftel, a pipelined variant that further accelerates mixed-trust execution. We implement both protocols atop Intel SGX and evaluate them in LAN and WAN environments. Our results show that Raftel achieves up to 625 TPS with sub-670 ms latency in WAN settings, outperforming HotStuff by up to 308 TPS in throughput while approaching the performance of fully TEE-assisted protocols.