Vulnerabilities of smart contracts and solutions

Abstract

In recent decade, blockchain concept was proposed in cryptocurrency, completion of transition without any third party. Today, this concept is being used in all possible applications like e-healthcare, transportation, communication, etc. In general, blockchain technology uses the concept of smart contract to transfer any money to end user. Smart contracts provide efficient performance of credible transactions (trackable and irreversible functionality) without involving third parties. These contracts are self-executing contracts with the terms of the agreement between buyer and seller. Note that smart contracts have distributed, decentralized blockchain network. Some applications of smart contacts are the following: land records, cryptocurrencies like Bitcoin, Ethereum, etc. With this much popularity of smart contract, today we are facing many vulnerabilities on such contract, for example, today's potential vulnerabilities are nearly 30% on smart contracts (examined by national university of Singapore). It is a critical issue and legitimate (valid) cause for having concern in the blockchain technology and we should take care about such critical issue because people's money or information are being shared through such smart contracts. In general, security vulnerabilities in software can be fixed by patching, but patching security vulnerabilities of decentralized applications on the Ethereum blockchain is not so straightforward. Due to the immutable nature of smart contracts, it is very difficult to upgrade the already deployed contracts. But, having the availability of smart contract as public, chances of vulnerability are higher on stored smart contracts. Hence, this chapter provides several mitigated critical smart contract vulnerabilities (in the past decade), possible technique to detect vulnerabilities on smart contract, and possible suggestions including opportunity (and research gaps) for future toward protecting smart contract code or agreement.