The libSRTP library is an open-source implementation of the Secure Real-time Transport Protocol (SRTP) originally authored by Cisco Systems, Inc. It is available under a BSD-style license.

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SRTP is a security profile for RTP that adds confidentiality, message authentication, and replay protection to that protocol. It is specified in RFC 3711. More information on the SRTP protocol itself can be found on the Secure RTP Page. Frequently Asked Questions are answered in the SRTP FAQ.

The libSRTP distribution is a .tgz file containing C source code. To get started do the following (using the latest version of the distribution available for download): 

gunzip srtp-X.Y.Z.tgz 
tar xvf srtp-X.Y.Z.tar 
cd srtp 
autoconf 
./configure 
make 

For information on how to build the library and run the test driver and example programs, see the libSRTP Overview and Reference Manual, which is included in the distribution as doc/libsrtp.pdf. The manual documents the Application Programming Interface (API) for the library. Please note that the README file in the distribution is somewhat out of date.

Libsrtp is graciously hosted by sourceforge.net. 

The initial implementation of libsrtp was done by David McGrew of the Cisco Systems, Inc. Advanced Crypto Development Group.