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zeekay
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Restructured from flat .tex/.pdf files into per-paper subdirectories. Added Antje Worring as co-author on all papers. Synced PDFs to pdfs/ for download site.
33 lines
1.7 KiB
TeX
33 lines
1.7 KiB
TeX
\section{Why Formal Verification}
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Software testing can show the presence of bugs, never their absence. For blockchain systems
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where bugs cause irreversible fund loss, this is insufficient. Formal verification uses
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mathematical proof to establish that a program or protocol satisfies its specification for
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\emph{all} inputs, not just the ones a test suite happens to exercise.
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\subsection{The Cost of Bugs in Blockchain}
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The DAO hack (2016, \$60M), Wormhole bridge exploit (2022, \$320M), and Ronin bridge
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compromise (2022, \$625M) share a common pattern: the vulnerable code was tested, audited,
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and deployed by competent teams. Testing and auditing are necessary but not sufficient.
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Formal verification closes the gap by providing machine-checked guarantees.
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\subsection{Why Not Just Test More?}
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Consider a BFT consensus protocol with $n$ validators. Testing safety requires exploring
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an exponential state space: $2^n$ possible failure combinations, arbitrary message
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reorderings, unbounded network delays. Even property-based testing with millions of random
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inputs covers a negligible fraction of this space. Formal proof covers it all by reasoning
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about the structure of the state space rather than sampling points within it.
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\subsection{Proof Assistants vs.\ Pen-and-Paper Proofs}
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Peer-reviewed papers in distributed systems regularly contain subtle errors in their proofs.
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Hawblitzel et al.\ found errors in published proofs of Paxos variants. A proof assistant
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like Lean~4 mechanically checks every step: if the proof compiles, the theorem holds
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(modulo the axioms of the underlying logic, which for Lean~4 is the Calculus of Inductive
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Constructions plus propositional extensionality and quotient types).
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%% ============================================================
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