PGPfone was a secure voice telephony system developed by Philip Zimmermann in 1995. The PGPfone protocol had little in common with Zimmermann's popular PGP email encryption package, except for the use of the name. It used ephemeral Diffie-Hellman protocol to establish a session key, which was then used to encrypt the stream of voice packets. The two parties compared a short authentication string to detect a Man-in-the-middle attack , which is the most common method of wiretapping secure phones of this type. PGPfone could be used point-to-point (with two modems ) over the public switched telephone network, or over the Internet as an early Voice over IP system.
5-539: In 1996, there were no protocol standards for Voice over IP. Ten years later, Zimmermann released the successor to PGPfone, Zfone and ZRTP , a newer and secure VoIP protocol based on modern VoIP standards. Zfone builds on the ideas of PGPfone. According to the MIT PGPfone web page, "MIT is no longer distributing PGPfone. Given that the software has not been maintained since 1997, we doubt it would run on most modern systems." This cryptography-related article
10-701: Is a stub . You can help Misplaced Pages by expanding it . This article related to telephony is a stub . You can help Misplaced Pages by expanding it . Zfone Zfone is software for secure voice communication over the Internet ( VoIP ), using the ZRTP protocol. It is created by Phil Zimmermann , the creator of the PGP encryption software. Zfone works on top of existing SIP - and RTP -programs, but should work with any SIP- and RTP-compliant VoIP-program. Zfone turns many existing VoIP clients into secure phones. It runs in
15-559: The AGPL. The parts of Zfone that are not part of the libZRTP SDK libraries are not licensed under the AGPL or any other open source license. Although the source code of those components is published for peer review, they remain proprietary. The Zfone proprietary license also contains a time bomb provision. It appears that Zfone development has stagnated, however, as the most recent version was released on 22 Mar 2009. In addition, since 29 Jan 2011, it has not been possible to download Zfone from
20-544: The Internet Protocol stack on any Windows XP, Mac OS X, or Linux PC, and intercepts and filters all the VoIP packets as they go in and out of the machine, and secures the call on the fly. A variety of different software VoIP clients can be used to make a VoIP call. The Zfone software detects when the call starts, and initiates a cryptographic key agreement between the two parties, and then proceeds to encrypt and decrypt
25-507: The voice packets on the fly. It has its own separate GUI , telling the user if the call is secure. Zfone describes itself to end-users as a "bump on the wire" between the VoIP client and the Internet, which acts upon the protocol stack. Zfone's libZRTP SDK libraries are released under either the Affero General Public License (AGPL) or a commercial license. Note that only the libZRTP SDK libraries are provided under
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