Public-key certificates are managed by a combination of the informal web of trust and the use of servers maintained by organizations. Prompt and reliable distribution of revocation notices is an essential ingredient for security in a public-key infrastructure. Current schemes based on certificate revocation lists on key servers are inadequate. An approach based on distributing revocation notices to "dependers" on each certificate, with cascading forwarding, is suggested. Research is necessary to investigate architectural issues, particularly reliability and response time analysis.

• needs.ps