In blockchain networks, so-called "full nodes" serve data to and relay transactions from clients through an RPC interface. This serving layer enables integration of "Web3" data, stored on blockchains, with "Web2" mobile or web applications that cannot directly participate as peers in a blockchain network. In practice, the serving layer is dominated by a small number of centralized services ("node providers") that offer permissioned access to RPC endpoints. Clients register with these providers because they offer reliable and convenient access to blockchain data: operating a full node themselves requires significant computational and storage resources, and public (permissionless) RPC nodes lack financial incentives to serve large numbers of clients with consistent performance. Permissioned access to an otherwise permissionless blockchain network raises concerns regarding the privacy, integrity, and availability of data access. To address this, we propose a Permissionless Accountable RPC Protocol (PARP). It enables clients and full nodes to interact pseudonymously while keeping both parties accountable. PARP leverages "light client" schemes for essential data integrity checks, combined with fraud proofs, to keep full nodes honest and accountable. It integrates payment channels to facilitate micro-payments, holding clients accountable for the resources they consume and providing an economic incentive for full nodes to serve. Our prototype implementation for Ethereum demonstrates the feasibility of PARP, and we quantify its overhead compared to the base RPC protocol.

翻译：在区块链网络中，所谓的“全节点”通过RPC接口向客户端提供数据并转发交易。该服务层实现了存储在区块链上的“Web3”数据与无法直接作为对等节点参与区块链网络的“Web2”移动或网络应用的集成。实践中，服务层主要由少数中心化服务提供商（“节点服务商”）主导，这些服务商提供需许可访问的RPC端点。客户端向这些提供商注册，因为它们提供可靠便捷的区块链数据访问：自行运行全节点需要大量计算和存储资源，而公共（无许可）RPC节点缺乏为大量客户端提供稳定性能的经济激励。对本质上无许可的区块链网络实施许可访问引发了数据访问的隐私性、完整性和可用性方面的担忧。为解决此问题，我们提出一种无许可可追责RPC协议（PARP）。该协议使客户端与全节点能够以匿名方式交互，同时保持双方的可追责性。PARP利用“轻客户端”方案进行必要的数据完整性检查，并结合欺诈证明机制，确保全节点保持诚实与可追责。协议集成支付通道以支持微支付，既使客户端对其消耗的资源负责，又为全节点提供服务提供经济激励。我们针对以太坊的原型实现验证了PARP的可行性，并通过量化其相较于基础RPC协议的开销进行评估。