Certificate-Based Encryption and the Certificate Revocation Problem

We introduce the notion of certificate-based encryption. In this model, a certificate – or, more generally, a signature – acts not only as a certificate but also as a decryption key. To decrypt a message, a keyholder needs both its secret key and an up-to-date certificate from its CA (or a signature from an authorizer). Certificate-based encryption combines the best aspects of identity-based encryption (implicit certification) and public key encryption (no escrow). We demonstrate how certificate-based encryption can be used to construct an efficient PKI requiring less infrastructure than previous proposals, including Micali’s Novomodo, Naor-Nissim and Aiello-Lodha-Ostrovsky. Comment: This is a version of the Eurocrypt 2003 paper, identical except for this comment and a correction in Section 3.2. I’m posting it online to make it more widely available, particularly since a couple of recent works propose essentially the same idea.