A Solicitous Approach to Smart Contract Verification

Abstract

Smart contracts are tempting targets of attacks, since they often hold and manipulate significant financial assets, are immutable after deployment, and have publicly available source code, with assets estimated in the order of millions of US Dollars being lost in the past due to vulnerabilities. Formal verification is thus a necessity, but smart contracts challenge the existing highly efficient techniques routinely applied in the symbolic verification of software, due to specificities not present in general programming languages. A common feature of existing works in this area is the attempt to reuse off-the-shelf verification tools designed for general programming languages. This reuse can lead to inefficiency and potentially unsound results, since domain translation is required. In this paper we describe a carefully crafted approach that directly models the central aspects of smart contracts natively, going from the contract to its logical representation without intermediary steps. We use the expressive and highly automatable logic of constrained Horn clauses for modeling and we instantiate our approach to the Solidity language. A tool implementing our approach, called Solicitous, was developed and integrated into the SMTChecker module of the Solidity compiler solc. We evaluated our approach on an extensive benchmark set containing 22446 real-world smart contracts deployed on the Ethereum blockchain over a 27 months period. The results show that our approach is able to establish safety of significantly more contracts than comparable, publicly available verification tools, with an order of magnitude increase in the percentage of formally verified contracts.

Scaling CheckMate for Game-Theoretic Security

“…CheckMate complements the state of the art in protocol verification with game-theoretic security analysis, providing economic security guarantees in addition to algorithmic correctness. CheckMate differs from existing static analyzers [4,8,16] of Ethereum smart contracts, as these techniques merely consider cryptographic security and formally verify the Solidity [1] implementation of smart contracts. Formal methods are also used in the cryptographic verification of more general protocols [2,10,14], yet without game-theoretic considerations.…”

“…Once deployed on the blockchain, vulnerabilities cannot be corrected and have the potential for significant monetary loss. Various existing approaches for the analysis and verification of blockchain protocols [2,4,8,14,16,19,20] focus on cryptographic and algorithmic correctness or, in other words, whether it is possible to steal assets or gain secret information. However, economic aspects must also be considered: whether it is possible for a group of users to profit from unintended behavior within the protocol itself, leading to vulnerabilities [12].…”