With Common IMS it has become possible to use IMS over a wide variety of access networks. These access networks provide security of varying strengths, or, in some cases, no security at all. It is therefore desirable to have a standard for IMS media plane security, which provides uniform protection of IMS media against eavesdropping and undetected modification across access networks. Furthermore, media transport in the core network, although generally less vulnerable than in the access network, may also be realised in varying ways with different guarantees of protection. It is therefore also desirable to have a standard for IMS media plane security, which guarantees protection of IMS media against eavesdropping and undetected modification in an end-to-end (e2e) fashion between two terminal devices.

The present document presents IMS media plane security for RTP and MSRP based media, IMS data channels (i.e., SCTP over DTLS) as well as security for BFCP as used in IMS conferencing. The security mechanisms are designed to meet the following three main objectives:

1. to provide security for media usable across all access networks
2. to provide an end-to-end (e2e) media security solution for RTP and data channel-based media to satisfy major user categories
3. to provide end-to-end (e2e) media security for important user groups like enterprises, National Security and Public Safety (NSPS) organizations and different government authorities who may have weaker trust in the inherent IMS security and/or may desire to provide their own key management service.

The media plane security for RTP based media is based on the well-established protocol SRTP. Key management solutions for SRTP are defined in this specification. The media plane security for MSRP, used in session-based messaging, is based on TLS. TLS is also used to protect BFCP. Key management solutions for MSRP and BFCP security are defined in the present document. The media plane security for IMS data channels, i.e., SCTP over DTLS, is based on DTLS. Two normative Annexes to the present document address IMS media plane security for immediate messaging and conferencing, respectively. The media plane security for session-based messaging is addressed in the main body of this specification.

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.

• References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
• For a specific reference, subsequent revisions do not apply.
• For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.