Cryptology ePrint Archive: Report 2022/384

Light Clients for Lazy Blockchains

Ertem Nusret Tas and Dionysis Zindros and Lei Yang and David Tse

Abstract: Decoupling consensus from transaction verification and execution is an important technique to increase the throughput of blockchains, a technique known as a lazy blockchain. Lazy blockchains can end up containing invalid transactions such as double spends, but these can easily be filtered out by full nodes that can check if there have been previous conflicting transactions. However, creating light (SPV) clients that do not see the whole transaction history on top of these chains 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 only 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 we illustrate how it can be applied to both the UTXO as well as the account based models. Lastly, we empirically demonstrate the feasibility of our scheme by providing experimental results.

Category / Keywords: cryptographic protocols / blockchains, lazy blockchains, interactive verification games, refereed computation

Date: received 24 Mar 2022, last revised 30 Mar 2022

Contact author: nusret at stanford edu, dionyziz at stanford edu, leiy at csail mit edu, dntse at stanford edu

Available format(s): PDF | BibTeX Citation

Note: 6 figures, 2 tables.

Version: 20220330:010307 (All versions of this report)

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