SRTP (Secure Real-time Transport Protocol)

An encrypted extension of RTP that provides confidentiality, authentication, and replay protection for voice and video media streams. SRTP uses AES encryption with keys derived from a master key exchanged out-of-band via DTLS-SRTP (WebRTC) or SDES (SIP). Unlike TLS which encrypts the transport layer, SRTP encrypts the RTP payload and authenticates the header, enabling end-to-end media encryption even through SRTP-aware NAT traversal proxies.