Feasibility of Cross-Chain Payment with Success Guarantees

TL;DR

This paper explores the feasibility of secure cross-chain payments with success guarantees, demonstrating solutions under synchrony assumptions and a weaker, asynchronous variant with Byzantine failures, advancing the understanding of trustless digital asset transfers.

Contribution

It introduces a new approach to cross-chain payments that guarantees success under synchrony and proposes a weaker asynchronous solution resilient to Byzantine failures.

Findings

Successful cross-chain payments are possible under synchrony assumptions.

A weaker asynchronous variant can be achieved with participant patience and Byzantine fault tolerance.

The work clarifies the relationship between cross-chain payments and cross-chain deals.

Abstract

We consider the problem of cross-chain payment whereby customers of different escrows---implemented by a bank or a blockchain smart contract---successfully transfer digital assets without trusting each other. Prior to this work, cross-chain payment problems did not require this success, or any form of progress. We demonstrate that it is possible to solve this problem when assuming synchrony, in the sense that each message is guaranteed to arrive within a known amount of time, but impossible to solve without assuming synchrony. Yet, we solve a weaker variant of this problem, where success is conditional on the patience of the participants, without assuming synchrony, and in the presence of Byzantine failures. We also discuss the relation with the recently defined cross-chain deals.