Abstract
Recently, real-world attacks against the web Public Key Infrastructure (PKI) have arisen more frequently. The current PKI that use Registration Authorities/Certificate Authorities (RAs/CAs) model suffer from notorious security vulnerabilities. Most of these vulnerabilities are due to compromises of RAs, which lead to impersonation attacks resulting in CAs misbehaving to issue bogus certificates. To counter this problem, many approaches, such as Certificate Transparency (CT), ARPKI, and PoliCert, have been proposed. Nonetheless, no solution has yet gained widespread acceptance as a result of complexity and deployability issues. Moreover, existing approaches still require to satisfy complicated interactions and synchronisation among the entities that are involved during certificate issuance, updates, and revocations. In this paper, we propose a new Blockchain-Based PKI (BB-PKI) to address these vulnerabilities of CA misbehaviour caused by impersonation attacks against RAs. Certificate Issuance Request (CIR) should be vouched by manifold RAs. Multiple CAs shall sign and issue the certificate using an out-of-band secure communication channel. Any RA that contributes to the verification process of a user's request can publish the certificate in the blockchain by creating a smart contract certificate transaction. BB-PKI offers strong security guarantees, compromising n - 1 of the RAs or CAs is not enough to launch impersonation attacks, meaning that attackers cannot compromise more than the threshold of the latter signatures to launch an attack.