SRTP (Secure Real-time Transport Protocol)

Also known as: Secure RTP, RFC 3711

SRTP is the IETF profile of RTP (RFC 3711) that provides confidentiality, message authentication and replay protection for real-time media streams. In IMS, SRTP is used to protect voice and video media between UEs and SBCs, between SBCs at interconnect, and for Wi-Fi Calling. Key material is typically established via SDES in older deployments or DTLS-SRTP in modern ones. SRTP is complementary to signalling-plane protections such as SIP over TLS or IPsec.

Categories: Security ControlsProtocols and StandardsEncryption and Cryptography

SRTP in context

Security controls in telecom span signaling firewalls (SS7/Diameter/GTP screening at the network edge), transport encryption (IPsec, TLS, PRINS), identity and access on OSS/BSS, and monitoring at both the packet and log level. Controls are audited against GSMA FS.11/FS.19/FS.20/FS.36 and, in Europe, NIS2 sectoral rules.

Telecom security is written into standards from 3GPP, GSMA, ETSI, IETF and ITU-T. Understanding which body owns which specification, and how the specs interlock (for example 3GPP TS 33.501 with GSMA FS.34 for 5G SBA security), is essential for both design and audit work.

To place SRTP in the wider telecom-security picture, review DTLS-SRTP, SIP Digest, HKDF, VPN, NAF and MACsec.

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