Decentralized Public Key Infrastructures atop Blockchain

The public key infrastructure (PKi) has been widely adopted to create, manage, distribute, store and revoke digital certificates, which plays an important role in bootstrapping secure communications. A PKi system authenticates entities with the corresponding public keys and it lays the security foundation for public-key cryptosystems in public-key encryption and digital signatures. However, traditional PKi systems suffer from security breaches, such as single-point-offailure and man-in-the-middle attacks due to the existence of a centralized certificate authority. in this article, we review the traditional centralized PKi system as well as the subjected security concerns, and then we propose possible solutions to address these issues with the emerging blockchain technology. Two frameworks are presented where blockchain is utilized as a public bulletin board or trusted majority. We implement the functions to evaluate the off-chain time costs and on-chain gas costs of the proposal, which demonstrate the feasibility and practicality of the proposal.