SYSTEM FOR ENSURING THAT THE BLINDING OF SECRET-KEY CERTIFICATES IS RESTRICTED, EVEN IF THE ISSUING PROTOCOL IS PERFORMED IN PARALLEL MODE

A cryptographic method is disclosed that enables the issuer in a secret-key certificate issuing protocol to issue triples consisting of a secret key, a corresponding public key, and a secret-key certificate of the issuer on the public key, in such a way that receiving parties can blind the public key and the certificate, but cannot blind a predetermined non-trivial predicate of the secret key even when executions of the issuing protocol are performed in parallel.