I think it's better than the other approaches to secure VoIP, because itachieves security without reliance on a PKI, key certification, trustmodels, certificate authorities, or key management complexity thatbedevils the email encryption world. It also does not rely on SIPsignaling for the key management, and in fact does not rely on anyservers at all. It performs its key agreements and key management in apurely peer-to-peer manner over the RTP packet stream. It interoperateswith any standard SIP phone, but naturally only encrypts the call if youare calling another Zfone client. This new protocol has been submittedto the IETF as a proposal for a public standard, to enableinteroperability of SIP endpoints from different vendors. Zfone has been tested with these VoIP clients and VoIP services: VoIP clients: X-Lite, Gizmo, and SJphone. VoIP service providers: Free World Dialup, iptel.org, and SIPphone.