Phil Zimmermann, the creator of Pretty Good Privacy (PGP), has developed new encryption software to make secure phone calls. The program is called Zfone, and it's designed to work with VoIP clients that use the industry standard SIP protocol.
On March 14, Zimmermann released a beta version of the widely anticipated Zfone. The software is currently available only for OS X (Tiger) and Linux, though a Windows version is due in April.
The open-source software manages cryptographic handshakes invisibly, and encrypts and decrypts voice calls as the traffic leaves and enters the computer. Operation is simple, and users don't have to agree in advance on an encryption key or type out long passcodes to make it work.
More details about this program can be read at