HKDF (HMAC-based Key Derivation Function)

Also known as: HMAC-based KDF

HKDF (RFC 5869) is a two-step extract-then-expand KDF built on HMAC. It is the standard KDF for TLS 1.3, IKEv2, Noise and modern secure messaging, and is used inside 5G SBA where TLS 1.3 traffic keys are derived. HKDF provides strong output separation through its info and salt parameters.

Categories: Security ControlsProtocols and StandardsEncryption and Cryptography

HKDF 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 HKDF in the wider telecom-security picture, review DTLS-SRTP, XMPP, SRTP, NAF, VPN and HTTPS.

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