Blockchain applications often rely on lightweight clients to access and verify on-chain data efficiently without the need to run a resource-intensive full node. These light clients must maintain robust security to protect the blockchain's integrity for users of applications built upon it, achieving this with minimal resources and without significant latency. Moreover, different applications have varying security needs. This work focuses on addressing these two key requirements in the context of Proof-of-Stake (PoS) blockchains and identifying the fundamental cost-latency trade-offs to achieve tailored, optimal security for each light client. The key security guarantee of PoS blockchains is economic (implied by the "stake"). In this paper we formalize this cryptoeconomic security to light clients, ensuring that the cost of corrupting the data provided to light clients must outweigh the potential profit, thereby economically deterring malicious actors. We further introduce "insured" cryptoeconomic security to light clients, providing unconditional protection via the attribution of adversarial actions and the consequent slashing of stakes. The divisible and fungible nature of stake facilitates programmable security, allowing for customization of the security level and insurance amount according to the specific needs of different applications. We implemented the protocols in less than 1000 lines of Solidity and TypeScript code and evaluated their gas cost, latency, and the computational overhead. For example, for a transaction with value of \$32k, the light client can choose between zero cost with a latency of 5 hours or instant confirmation with an insurance cost of \$7.45. Thus, the client can select the optimal point on the latency-cost trade-off spectrum that best aligns with its needs. Light clients require negligible storage and face minimal computational costs,...

翻译：区块链应用通常依赖轻客户端高效访问和验证链上数据，而无需运行资源密集型全节点。这些轻客户端必须维持强大的安全性，以保护基于区块链构建的应用用户的链上数据完整性，同时以最少资源实现且无显著延迟。此外，不同应用对安全性有不同需求。本研究聚焦于在权益证明（PoS）区块链背景下解决这两个关键需求，并识别实现每个轻客户端定制化最优安全性的基础成本-延迟权衡。PoS 区块链的关键安全保证是经济性的（由“权益”隐含）。本文形式化了面向轻客户端的加密经济安全性，确保破坏提供给轻客户端数据的成本超过潜在收益，从而在经济上威慑恶意行为者。我们进一步将“保险式”加密经济安全性引入轻客户端，通过归因对抗行为并随之削减权益提供无条件保护。权益的可分性和可替代性促进了可编程安全性，允许根据特定应用需求定制安全级别和保险金额。我们以不到1000行Solidity和TypeScript代码实现了协议，并评估了其Gas成本、延迟和计算开销。例如，对于价值3.2万美元的交易，轻客户端可选择零成本但延迟5小时，或即时确认但保险成本为7.45美元。因此，客户端可在延迟-成本权衡谱系中选择最符合其需求的最优点。轻客户端所需存储可忽略不计，且面临极低计算成本……