Quantitative Analysis of Smart Contracts

Krishnendu Chatterjee,Amir Kafshdar Goharshady,Yaron Velner

doi:10.1007/978-3-319-89884-1_26

Krishnendu Chatterjee, Amir Kafshdar Goharshady + Show 1 more

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https://doi.org/10.1007/978-3-319-89884-1_26

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Abstract

Smart contracts are computer programs that are executed by a network of mutually distrusting agents, without the need of an external trusted authority. Smart contracts handle and transfer assets of considerable value (in the form of crypto-currency like Bitcoin). Hence, it is crucial that their implementation is bug-free. We identify the utility (or expected payoff) of interacting with such smart contracts as the basic and canonical quantitative property for such contracts. We present a framework for such quantitative analysis of smart contracts. Such a formal framework poses new and novel research challenges in programming languages, as it requires modeling of game-theoretic aspects to analyze incentives for deviation from honest behavior and modeling utilities which are not specified as standard temporal properties such as safety and termination. While game-theoretic incentives have been analyzed in the security community, their analysis has been restricted to the very special case of stateless games. However, to analyze smart contracts, stateful analysis is required as it must account for the different program states of the protocol. Our main contributions are as follows: we present (i) a simplified programming language for smart contracts; (ii) an automatic translation of the programs to state-based games; (iii) an abstraction-refinement approach to solve such games; and (iv) experimental results on real-world-inspired smart contracts.

Highlights

In this work we present a quantitative stateful game-theoretic framework for formal analysis of smart-contracts.Smart Contracts
We show that many classical smart contracts can be described in our language, and a smart contract programmed in our language can be translated to Solidity [30], which is the most popular Ethereum smart contract language
In this work we present a programming language for smart contracts, and an abstraction-refinement approach for quantitative concurrent games to automatically analyze such contracts

Summary

Introduction

In this work we present a quantitative stateful game-theoretic framework for formal analysis of smart-contracts.Smart Contracts. Hundreds of crypto-currencies are in use today, and investments in them are increasing steadily [24]. These currencies are not controlled by any central authority like governments or banks, instead they are governed by the blockchain protocol, which dictates the rules and determines the outcomes, e.g., the validity of money transactions and account balances. Blockchain was initially used for peer-to-peer Bitcoin payments [43], but recently it is used for running programs (called smart contracts). A smart contract is a program that runs on the blockchain, which enforces its correct execution Ethereum [16] is a decentralized virtual machine, which runs programs called contracts. Contracts are written in a Turing-complete bytecode language, called Ethereum Virtual Machine (EVM) bytecode [53]. Each transaction may contain input parameters for the contract and an associated monetary amount, possibly 0, which is transferred from the user to the contract

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