Smart contracts are a kind of application with tamperproof context and clauses which are deployed and executed on blockchain networks. It means that no party (and even creators) are able to manipulate the codes and functions after deployment. Thus unlike traditional paper contracts or digital ones which are programmed on centralized platforms that are exposed to alteration, termination and deletion by a trusted party or a third person, smart contracts bring parties into agreement and generate a novel and powerful class of trust without relying on trust in any party or intermediaries. This feature turns smart contracts into a superior tool for realizing and implementing digital agreement.