Computationally Efficient Distributed and Delegated Certification

Certification in public key cryptographic applications concerns the involvement of a CA (Certifying Agent) in approving the validity of users´ public keys. Distributed certification pertains to the case where several CAs are involved in issuing certificates. This also includes the case of multi-attribute certification, where different CAs approve different user´s attributes. In delegated certification, agents transfer certificate issuing authority in hierarchical chain. Distributed, multi-attribute and delegated certification techniques having a low computational complexity are presented in this paper. It is shown how multiplicity aspects of the various applications are mapped into a multiplied exponents mathematical implementation of the form Pi_i=1 ^m A_i ^bi mod p, which is essentially equivalent to a single exponentiation for a moderate m. A fundamental feature of the presented procedures pertains to implementing distributed/multi-attribute certification by referring to any desired subset of participating CAs.