Lazy blockchains decouple consensus from transaction verification and execution to increase throughput. Although they can contain invalid transactions (e.g., double spends) as a result, these can easily be filtered out by full nodes that check if there have been previous conflicting transactions. However, creating light (SPV) clients that do not see the whole transaction history becomes a challenge: A record of a transaction on the chain does not necessarily entail transaction confirmation. In this paper, we devise a protocol that enables the creation of efficient light clients for lazy blockchains. The number of interaction rounds and the communication complexity of our protocol are logarithmic in the blockchain execution time. Our construction is based on a bisection game that traverses the Merkle tree containing the ledger of all - valid or invalid - transactions. We prove that our proof system is succinct, complete and sound, and empirically demonstrate the feasibility of our scheme.

翻译：懒区块链将共识与交易验证和执行解耦以提高吞吐量。尽管这可能导致包含无效交易（例如双重支付），但全节点通过检查是否存在先前的冲突交易，可以轻松过滤这些无效交易。然而，构建无法查看完整交易历史的轻量级（SPV）客户端变得具有挑战性：链上的交易记录并不必然意味着交易已确认。本文设计了一种协议，使得在懒区块链上创建高效的轻客户端成为可能。该协议的交互轮数和通信复杂度与区块链执行时间呈对数关系。我们的构造基于一个二分游戏，该游戏遍历包含所有交易（无论有效或无效）账本的默克尔树。我们证明了该证明系统具有简洁性、完备性和可靠性，并通过实验验证了方案的可行性。