A key server (320) based communication system (310) wherewith communicating parties, originators (312) and recipients (314), exchange encrypted communications (324). An originator requests or provides a key (330) to the key server, optionally with an assertion (322) from an authentication authority (318). Based on attributes (326) from the originator or elsewhere, the key server sets controlling events (340) for the communication. The originator encrypts and sends the communication to one or more recipients. A recipient may or may not request the key to decrypt the message. Positive events (342) are determined based on the controlling events and when and how many such requests occur. Negative events (344) are determined based on the absence of any requests or all requests being untimely.