Smart contracts are automated or self-enforcing contracts that can be used to
exchange assets without having to place trust in third parties. Many commercial
transactions use smart contracts due to their potential benefits in terms of
secure peer-to-peer transactions independent of external parties. Experience
shows that many commonly used smart contracts are vulnerable to serious
malicious attacks which may enable attackers to steal valuable assets of
involving parties. There is therefore a need to apply analysis and automated
repair techniques to detect and repair bugs in smart contracts before being
deployed. In this work, we present the first general-purpose automated smart
contract repair approach that is also gas-aware. Our repair method is
search-based and searches among mutations of the buggy contract. Our method
also considers the gas usage of the candidate patches by leveraging our novel
notion of gas dominance relationship. We have made our smart contract repair
tool SCRepair available open-source, for investigation by the wider community.

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