cisco/libsrtpLibrary for SRTP (Secure Realtime Transport Protocol)
This package provides an implementation of the Secure Real-time Transport Protocol (SRTP), the Universal Security Transform (UST), and a supporting cryptographic kernel. The SRTP API is documented in include/srtp.h, and the library is in libsrtp2.a (after compilation).
This document describes libSRTP, the Open Source Secure RTP library from Cisco Systems, Inc. RTP is the Real-time Transport Protocol, an IETF standard for the transport of real-time data such as telephony, audio, and video, defined by RFC 3550. Secure RTP (SRTP) is an RTP profile for providing confidentiality to RTP data and authentication to the RTP header and payload. SRTP is an IETF Standard, defined in RFC 3711, and was developed in the IETF Audio/Video Transport (AVT) Working Group. This library supports all of the mandatory features of SRTP, but not all of the optional features. See the Supported Features section for more detailed information.
This document is also used to generate the documentation files in the /doc/ folder where a more detailed reference to the libSRTP API and related functions can be created (requires installing doxygen.). The reference material is created automatically from comments embedded in some of the C header files. The documentation is organized into modules in order to improve its clarity. These modules do not directly correspond to files. An underlying cryptographic kernel provides much of the basic functionality of libSRTP but is mostly undocumented because it does its work behind the scenes.
[email protected] general mailing list for news / announcements / discussions. This is an open list, see https://lists.packetizer.com/mailman/listinfo/libsrtp for singing up.
[email protected] for disclosing security issues to the libsrtp maintenance team. This is a closed list but anyone can send to it.
libSRTP is distributed under the following license, which is included in the source code distribution. It is reproduced in the manual in case you got the library from another source.
Copyright (c) 2001-2017 Cisco Systems, Inc. All rights reserved.
Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
- Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
- Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
- Neither the name of the Cisco Systems, Inc. nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
libSRTP provides functions for protecting RTP and RTCP. RTP packets
can be encrypted and authenticated (using the srtp_protect()
function), turning them into SRTP packets. Similarly, SRTP packets
can be decrypted and have their authentication verified (using the
srtp_unprotect() function), turning them into RTP packets. Similar
functions apply security to RTCP packets.
The typedef srtp_stream_t points to a structure holding all of the
state associated with an SRTP stream, including the keys and
parameters for cipher and message authentication functions and the
anti-replay data. A particular srtp_stream_t holds the information
needed to protect a particular RTP and RTCP stream. This datatype
is intentionally opaque in order to better seperate the libSRTP
API from its implementation.
Within an SRTP session, there can be multiple streams, each
originating from a particular sender. Each source uses a distinct
stream context to protect the RTP and RTCP stream that it is
originating. The typedef srtp_t points to a structure holding all of
the state associated with an SRTP session. There can be multiple
stream contexts associated with a single srtp_t. A stream context
cannot exist indepent from an srtp_t, though of course an srtp_t can
be created that contains only a single stream context. A device
participating in an SRTP session must have a stream context for each
source in that session, so that it can process the data that it
receives from each sender.
In libSRTP, a session is created using the function srtp_create().
The policy to be implemented in the session is passed into this
function as an opaque srtp_policy_t handle. A single policy handle
describes one stream policy. To configure multiple streams, create a
session and add additional policies with srtp_stream_add().
