Zfone is a secure
VoIP phone software product which enables users to make encrypted phone calls over the Internet.
The principal designer of Zfone is Phil Zimmermann, the creator of
PGP.
Zfone utilizes a protocol called ZRTP, which performs its key agreements and key management in a pure peer-to-peer manner over the RTP media stream.
Zfone interoperates with any standard SIP phone, but naturally only encrypts the call if you are calling another ZRTP client.
Zfone is available as a "plugin" for a wide variety of existing VoIP clients, effectively converting them into secure phones. Zfone is also available as an SDK to allow VoIP product vendors to integrate encryption into their products.
Zfone uses 128- or 256-bit
AES together with a 3,000-bit key exchange system and voice based verification to prevent man in the middle attacks.
Zfone is available for Windows, Linux, and Mac OS X.
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