Borderware will become the first commercial licensee of Phil Zimmerman's Zfone encryption technology. Borderware intends to integrate the technology into its SIPassure voice-over-IP (VoIP) firewall solution.

Zimmermann, best known as the creator of of Pretty Good Privacy (PGP), developed Zfone as a solution for VoIP solutions that do not use their own encryption. Zfone sits in between a VoIP client and the Internet to encrypt communication between endpoints. One major advantage of using the ZRTP protocol is that it does not rely on a Public Key Infrastructure (PKI)..

Zfone uses Zimmerman's ZRTP protocol, which is a key agreement protocol designed as a set of header extensions to the Real-time Transport Protocol (RTP). ZRTP performs a Diffie-Hellman key exchange during the setup of a VoIP call. The result of the peer-to-peer exchange is a shared secret which is then used to generate encryption keys for a Secure RTP communication session.

Borderware's SIPassure firewall appliance protects applications that use the Session Initiation Protocol (SIP), which is commonly used for video conferencing, VoIP calls, games, and messaging applications. The appliance defends against DoS attacks, spoofiing, injections attacks, and provides access controls, quality of service (QoS) traffic shaping, monitoring, logging, and more.

"As VoIP grows into a replacement for the \[public switched telephone network\], we will absolutely need to protect it, or organized crime will be attacking it as intensively as they attack the rest of the Internet today," said Phil Zimmermann. "The combination of Zfone and BorderWare makes it easy to convert an entire installed base of office phones into secure phones in just one stroke, without having to replace them all with ZRTP-enabled phones."

Zimmerman, along with collegues Jon Callas and Alan Johnston, submitted ZRTP to the IETF as a proposal for a public standard, which he hopes will become accepted as a way to enable interoperability of SIP-based products from different vendors. Zimmerman also published a Zone Software Developer's Kit (SDK) that can be license by those who wish to integrate Zfone/ZRTP into their applications and hardware solutions.