In an infrastructure in which some of a plurality of entities provide
cryptographically supported services, a method of registering a
subscriber entity of a plurality of entities at a principal entity of a
plurality of entities, the method comprising the subscriber entity
requesting service from the principal entity by sending a request message
to a registrar entity of the plurality of entities; the registrar entity
verifying the subscriber entity and forwarding the request for service to
the principal entity; the principal entity storing the forwarded request
and transmitting an acknowledgement message to the registrar entity, the
acknowledgement stating acceptance and authentication/authorization
information that the subscriber entity requires for the requested
service; and the registrar entity verifying the authenticity of the
received acknowledgement message, and, if correct, forwarding the
acknowledgement message to the subscriber entity.