The Twinkle softphone package, immediately available with SRTP/ZRTP support, is the first complete free software package to make use of Secure call features offered in the GNU RTP Stack.
The GNU RTP stack can be used to develop secure communications for GNU/Linux hosted applications. The stack may also be used to develop application on various BSD systems including Mac OS/X, on Microsoft Windows, and even for embedded systems. We have tested and built the GNU RTP Stack with Handhelds Open Embedded build environment, and we look forward to implementing a Twinkle based secure calling solutions on Linux kernel powered cell phones in the future.
Securing RTP sessions is part of our vision in GNU Telephony to help make passive voice communication intercept a thing of the past. By making "secure by design" encryption capabilities simple to embed, and by enabling the largest possible participation in developing such solutions through free software, we hope to break down those remaining barriers that prevent secure telephony from being widely deployed over next generation telephone networks. Part of this vision includes offering TLS encapsulated SIP over TCP, and deployment of anonymous calling proxies, to further deny passive data mining of call session and connection associative information in the future.
Phil Zimmermann's zrtp specification; http://www.infosecwriters.com/text_resources/pdf/Z fone_SSotillo.pdf.
Zfone project; http://www.philzimmermann.com/zfoneproject/index.h tml.
GNU Telephony Secure Calling; http://wiki.gnutelephony.org/index.php/Secure_Call .
Twinkle Softphone; http://www.twinklephone.com/.
Open Embedded; http://www.handhelds.org/geeklog/index.php
About GNU Telephony:
GNU Telephony is a meta project dedicated to the development and promotion of the use of free software for telephony. GNU Telephony is used to directly support the GNU Common C++ family of libraries and telephony application servers such as GNU Bayonne, which are part of the GNU Project, as well as other packages that we regularly use. We will also support several special projects from this site, including CAPE runtime libraries, Secure Calling, and GNU Telephony Open Embedded."