With the increasing adoption of decentralized information systems based on a variety of permissionless blockchain networks, the choice of consensus mechanism is at the core of many controversial discussions. Ethereum's recent transition from (PoW) to proof-of-stake (PoS)-based consensus has further fueled the debate on which mechanism is more favorable. While the aspects of energy consumption and degree of (de-)centralization are often emphasized in the public discourse, seminal research has also shed light on the formal security aspects of both approaches individually. However, related work has not yet comprehensively structured the knowledge about the security properties of PoW and PoS. Rather, it has focused on in-depth analyses of specific protocols or high-level comparative reviews covering a broad range of consensus mechanisms. To fill this gap and unravel the commonalities and discrepancies between the formal security properties of PoW- and PoS-based consensus, we conduct a systematic literature review over 26 research articles. Our findings indicate that PoW-based consensus with the longest chain rule provides the strongest formal security guarantees. Nonetheless, PoS can achieve similar guarantees when addressing its more pronounced tradeoff between safety and liveness through hybrid approaches.

翻译：随着基于各类无许可区块链网络的去中心化信息系统日益普及，共识机制的选择成为诸多争议性讨论的核心。以太坊近期从工作量证明（PoW）向权益证明（PoS）共识的转变，进一步加剧了关于哪种机制更优的辩论。虽然公众讨论中常强调能耗与去中心化程度等维度，但开创性研究也已分别从形式安全角度对两种方法进行了深入剖析。然而，现有工作尚未系统梳理PoW与PoS安全属性的相关知识结构，而是聚焦于特定协议深度分析或涵盖广泛共识机制的高层次比较综述。为填补这一空白并揭示基于PoW与PoS共识的形式安全性共性与差异，我们对26篇研究论文进行了系统性文献回顾。研究结果表明，采用最长链规则的PoW共识能提供最强的形式安全保证。尽管如此，PoS通过混合方法处理其安全性与活性之间更显著权衡时，仍可达到类似的安全保障水平。