Hephaestus: Modeling, Analysis, and Performance Evaluation of Cross-Chain Transactions

Ecosystems of multiple blockchains are now a reality. Multichain applications and protocols are perceived as necessary to enable scalability, privacy, and composability. Despite being a promising emerging area, we have been witnessing devastating attacks on cross-chain bridges that have caused billions of dollars in losses, and no apparent solution seems to emerge from the ongoing chaos. In this article, we present our contribution to minimizing bridge attacks, by monitoring a cross-chain model. In particular, we aggregate cross-chain events into cross-chain transactions, and verify if they follow a set of cross-chain rules, which then generate a model. We propose Hephaestus, the first cross-chain model generator that captures the operational complexity of cross-chain applications. Hephaestus can generate cross-chain models from local transactions in different ledgers, realizing arbitrary cross-chain use cases and allowing operators to monitor their applications. Monitoring helps identify outliers and malicious behavior, which can enable programmatically stopping attacks (“a circuit breaker”), including bridge hacks. We conduct a detailed evaluation of our system, where we implement a cross-chain bridge use case. Our experimental results show that Hephaestus can process 600 cross-chain transactions in less than 5.5 s in an environment with two blockchains using sublinear storage, paving the way for more resilient bridge designs.

I. Introduction

Recently, many initiatives and projects have appeared around the concept of blockchain interoperability (BI), where a multichain ecosystem is perceived as the enabler for a scalable and adaptable platform for various use cases [1], [2], [3], [4]. To enable such an ecosystem, bespoke distributed ledger technology (DLT) interoperability solutions, such as cross-chain bridges (or simply bridges), are used to connect heterogeneous DLTs, i.e., DLTs with different privacy, security, decentralization, and scalability properties [5]. The total value locked (TVL) in bridges peaked in March 2022, at around $30 billion worth of assets locked just in Ethereum (as the chain receiving the transferred assets) [6], [7], effectively reflecting the synergistic effects of free flow of capital, as now users can use their capital on multiple blockchains. As of September 2023, the TVL is still significant, collecting around 9B USD, as Fig. 1 shows. With more than 40 bridging projects [8], the trend is for projects to either mature by improving their security and usability or disappear.