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Security Fundamentals & Crypto · Intermediate

Secure Real-time Transport Protocol (SRTP)

Profile of RTP that provides encryption, authentication, and replay protection for voice and video streams.

Definition

SRTP (RFC 3711) protects media in VoIP and video conferencing, typically with AES and HMAC-SHA1 or AEAD modes. Keys are exchanged via SDES over TLS-protected SIP or via DTLS-SRTP, which WebRTC mandates. SIP signaling itself is secured with TLS (SIPS, port 5061).

Example

A VoIP system uses SIP over TLS on port 5061 and SRTP for call audio.

Exam tip

SRTP protects media; SIP over TLS protects signaling.

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