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.

SRTP is a security profile for RTP that adds confidentiality, message authentication, and replay protection to that protocol. It is specified in RFC 3711.

SRTP is ideal for protecting Voice over IP traffic because it can be used in conjunction with header compression and has no effect on IP Quality of Service. These facts provide significant advantages, especially for voice traffic using low-bitrate voice codecs such as G.729 and iLBC.