Zfone™ is a new secure VoIP phone software product which lets you make encrypted phone calls over the Internet. Its principal designer is Phil Zimmermann, the creator of PGP, the most widely used email encryption software in the world. Zfone uses a new protocol called ZRTP, which has a better architecture than the other approaches to secure VoIP.

* Doesn't depend on signaling protocols, PKI, or any servers at all. Key negotiations are purely peer-to-peer through the media stream * Interoperates with any SIP/RTP phone, auto-detects if encryption is supported by other endpoint * Available as a "plugin" for existing soft VoIP clients, effectively converting them into secure phones * Available as an SDK for developers to integrate into their VoIP applications * IETF has published the protocol spec as RFC 6189, and source code is published