PKI Safety Net (PKISN): Addressing the Too-Big-to-Be-Revoked Problem of the TLS Ecosystem
This addresses a critical security and privacy issue for users and systems relying on TLS certificates, though it is an incremental extension of existing mechanisms like Certificate Transparency.
The paper tackles the problem of revoking certificates from major certification authorities (CAs) in the TLS ecosystem, which is currently infeasible due to massive collateral damage, by proposing PKI Safety Net (PKISN), a system that uses publicly accessible logs for certificates and revocations, enabling simple deployment and complete implementation.
In a public-key infrastructure (PKI), clients must have an efficient and secure way to determine whether a certificate was revoked (by an entity considered as legitimate to do so), while preserving user privacy. A few certification authorities (CAs) are currently responsible for the issuance of the large majority of TLS certificates. These certificates are considered valid only if the certificate of the issuing CA is also valid. The certificates of these important CAs are effectively too big to be revoked, as revoking them would result in massive collateral damage. To solve this problem, we redesign the current revocation system with a novel approach that we call PKI Safety Net (PKISN), which uses publicly accessible logs to store certificates (in the spirit of Certificate Transparency) and revocations. The proposed system extends existing mechanisms, which enables simple deployment. Moreover, we present a complete implementation and evaluation of our scheme.