Recently, a novel peer sampling protocol, Elevator, was introduced to construct network topologies tailored for emerging decentralized applications such as federated learning and blockchain. Elevator builds hub-based topologies in a fully decentralized manner, randomly selecting hubs among participating nodes. These hubs, acting as central nodes connected to the entire network, can be leveraged to accelerate message dissemination. Simulation results have shown that Elevator converges rapidly (within 3--4 cycles) and exhibits robustness against crash failures and churn. However, its resilience to Byzantine adversaries has not been investigated. In this work, we provide the first evaluation of Elevator under Byzantine adversaries and show that even a small fraction (2%) of Byzantine nodes is sufficient to subvert the network. As a result, we introduce LIFT, a new protocol that extends Elevator by employing a cryptographically secure pseudo-random number generator (PRNG) for hub selection, thereby mitigating Byzantine manipulation. In contrast, LIFT withstands adversarial infiltration and remains robust with up to 10% Byzantine nodes. These results highlight the necessity of secure randomness in decentralized hub formation and position LIFT as a more reliable building block for Byzantine-resilient decentralized systems.

翻译：最近，一种新颖的对等采样协议Elevator被提出，用于构建面向新兴去中心化应用（如联邦学习和区块链）的网络拓扑。Elevator以完全去中心化的方式构建基于枢纽的拓扑结构，在参与节点中随机选择枢纽节点。这些枢纽节点作为连接整个网络的中心节点，可用于加速消息传播。仿真结果表明，Elevator收敛迅速（在3-4个周期内），并对崩溃故障和节点流失表现出鲁棒性。然而，其对拜占庭攻击的容错能力尚未得到研究。本文首次评估了Elevator在拜占庭攻击下的表现，结果表明即使仅有少量（2%）的拜占庭节点就足以破坏网络。为此，我们提出了LIFT协议，该协议通过采用密码学安全的伪随机数生成器进行枢纽选择来扩展Elevator，从而抵御拜占庭操纵。相比之下，LIFT能够抵抗敌手渗透，在高达10%的拜占庭节点存在时仍保持鲁棒性。这些结果凸显了安全随机性在去中心化枢纽形成中的必要性，并使LIFT成为构建拜占庭容错去中心化系统的更可靠基础组件。