Atomic Crosschain Transactions White Paper

TL;DR

This white paper introduces Atomic Crosschain Transaction technology enabling secure, atomic, and composable cross-blockchain interactions in Ethereum, avoiding reliance on traditional techniques like HTLCs or trusted intermediaries.

Contribution

It presents a novel crosschain transaction framework using BLS signatures and coordination contracts for secure, atomic, and composable inter-blockchain operations.

Findings

Supports synchronous and atomic cross-chain function calls

Uses BLS Threshold Signatures for validator consensus

Ensures execution validity through dynamic code analysis and signed nested transactions

Abstract

Atomic Crosschain Transaction technology allows composable programming across private Ethereum blockchains. It allows for inter-contract and inter-blockchain function calls that are both synchronous and atomic: if one part fails, the whole call graph of function calls is rolled back. It is not based on existing techniques such as Hash Time Locked Contracts, relay chains, block header transfer, or trusted intermediaries. BLS Threshold Signatures are used to prove to validators on one blockchain that information came from another blockchain and that a majority of the validators of that blockchain agree on the information. Coordination Contracts are used to manage the state of a Crosschain Transaction and as a repository of Blockchain Public Keys. Dynamic code analysis and signed nested transactions are used together with live argument checking to ensure execution only occurs if the execution results in valid state changes. Contract Locking and Lockability enable atomic updates.