BlockChain I/O: Enabling Cross-Chain Commerce

By enabling users to safely transfer digital tokens without trusted intermediaries, blockchains have fueled the rise of Decentralized Finance (DeFi). However, the current DeFi ecosystem consists of multiple independent blockchains, and cross-chain token trading is a challenge because the desirable properties of individual blockchains do not always generalize to a multi-chain setting. Recently, advances have been made in the generalization of these properties, but there is still a lack of an overarching framework that provides the full set of properties required for practical cross-chain commerce: transaction atomicity, stablecoin support, privacy-preserving digital identities, and general applicability. In this paper, we present BlockChain I/O to provide such a framework. BlockChain I/O uses entities called cross-chain services to relay information between different chains. Cross-chain services cannot violate transaction atomicity, and are disincentivized from other types of misbehavior -- i.e., causing delays or misrepresenting information -- through an audit system. BlockChain I/O uses stablecoins to mitigate price fluctuations, and a Digital ID system to allow users to prove aspects of their identity without violating privacy. After presenting the core architecture of BlockChain I/O, we demonstrate how to use it to implement a cross-chain marketplace. Finally, we use an experimental evaluation to demonstrate BlockChain I/O's practical performance.