An Examination Protocol for Handling Programmable Answers Using a Public Blockchain

Abstract

Examinations that involve programming, such as programming contests and certification exams, are common. However, current examination protocols require full trust in the operating organizations, which allows malicious organizations to cheat. As a countermeasure, efforts are being made to develop examination protocols that do not need a trusted authority. One way to build such a decentralized protocol is to apply blockchain. Several blockchain-based examination protocols have been proposed, but they can only handle a finite set of correct answers. We propose an examination protocol that can handle a set of correct answers defined by a program and mathematically guarantee the validity of the protocol. We also implement a programming contest platform based on the proposed method on Ethereum and show the feasibility of the method. Furthermore, we measure the economic cost of the method using the implementation and confirm that the method is feasible for approximately 30–40 USD.