  Voice Service Providers (VSPs) participating in VoIP peering frequently want
to withhold their identity and related privacy-sensitive information from other
parties during the VoIP communication. A number of existing documents on VoIP
privacy exist, but most of them focus on end user privacy. By summarizing and
extending existing work, we present a unified privacy mechanism for both VoIP
users and service providers. We also show a case study on how VSPs can use this
mechanism for identity and topology hiding in VoIP peering.
