An online conference session management system includes computer sites associated with a conference session holder, a plurality of service providers and a plurality of conference session participants. The conference session holder and each service provider has a respective associated public/private key pair for a specified online conference session. Each service provider is provided with an active participant registration certificate that gives the service provider the authority to register participants of the specified conference session, as well as authority to register other service providers as active participants of the specified conference session by providing those other service providers with respective active participant registration certificates. Each active participant registration certificate is digitally signed by either the conference session holder or one of the service providers using a private key of a public/private key pair unique to the conference session holder or respective service provider. Each active participant registration certificate includes the public key of the public/private key pair unique to the service provider whose authority to register participants is given by that active participant registration certificate. The service providers provide participants of the specified conference session with passive participant registration certificates. Each passive participant registration certificate is digitally signed by a service provider using a private key associated with that service provider. A passive participant registration certificate is validated by verifying the certificate's digital signature with the public key associated with the service provider that provided the passive participant registration certificate, and then validating that service provider's active participant registration certificate.