A Comparison of Blockchain-based PKI Implementations

Abstract

Blockchain technology has recently been proposed by many authors for decentralized key management in the context of Public Key Infrastructures (PKIs). Instead of relying on trusted key servers – centralized or decentralized –, the confirmation and revocation of keys is distributed over a multitude of participants. A pletheora of implementations exist, all of which rely on different properties of blockchains. In this paper, we motivate the most relevant properties of blockchains as well as PKI and how they are linked. Furthermore, we provide an overview of state-of-the-art blockchain-based PKI implementations and compare them with respect to these properties. While all analyzed implementations fullfil the basic requirements of PKIs, we find that (i) privacy is very often neglected; and (ii) only a small subset is evaluated with respect to both, complexity and cost. In order to provide a guideline for future blockchain-based PKI implementations, we conclude with a set of recommendations based on our findings.