H04L 9/3265

{Cryptographic mechanisms or cryptographic} arrangements for secret or secure communication including means for verifying the identity or authority of a user of the system {or for message authentication, e.g. authorization, entity authentication, data integrity or data verification, non-repudiation, key authentication or verification of credentials involving certificates, e.g. public key certificate [PKC] or attribute certificate [AC]; Public key infrastructure [PKI] arrangements using certificate chains, trees or paths; Hierarchical trust model}