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\title{Hephaestus: Modelling, Analysis, and Performance Evaluation of
Cross-Chain Transactions}



\author[1,1,1]{Rafael Belchior }%
\author[2]{Peter Somogyvari }%
\author[2]{Jonas Pfannschmid }%
\author[2]{André Vasconcelos }%
\author[2]{Miguel Correia }%
\affil[1]{Blockdaemon; INESC-ID}%
\affil[2]{Affiliation not available}%


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  \date{May 07, 2026}


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\begin{abstract}
Ecosystems of multiple blockchains are now a reality. Multi-chain
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
paper, we present our contribution to minimizing bridge attacks, by
monitoring a \emph{cross-chain model}. In particular, we aggregate
\emph{cross-chain events} into \emph{cross-chain transactions}, and
verify if they follow a set of \emph{cross-chain rules}, which then
generate a model.

We propose \textbf{Hephaestus}, the first cross-chain model generator
that captures the operational complexity of cross-chain applications.
\textbf{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.\selectlanguage{ngerman}Â

We conduct a detailed evaluation of our system, where we implement a
cross-chain bridge use case. Our experimental results show that
\textbf{Hephaestus} can process 600 cross-chain transactions in less
than 5.5 seconds in an environment with two blockchains using sublinear
storage, paving the way for more resilient bridge designs.%
\end{abstract}\selectlanguage{ngerman}%



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