HKDF (HMAC-based Key Derivation Function)
Was ist HKDF (HMAC-based Key Derivation Function)?
HKDF (HMAC-based Key Derivation Function)An extract-then-expand key derivation function based on HMAC, specified in RFC 5869, designed to turn high-entropy but non-uniform secret material (DH shared secrets, master keys) into multiple cryptographically strong keys.
HKDF (HMAC-based Key Derivation Function), defined by Krawczyk in RFC 5869 (2010), is the default modern KDF for symmetric key derivation from already-high-entropy inputs such as Diffie-Hellman shared secrets, master keys, or pre-shared keys. It is built in two phases. Extract takes input keying material (IKM) and an optional salt and applies HMAC to produce a fixed-length pseudorandom key (PRK). Expand then applies HMAC iteratively, with a counter and an info-context parameter, to derive output keying material of arbitrary length. The info parameter is used to bind derived keys to a context, which makes it safe to derive many independent keys from one PRK without collision. HKDF is the KDF chosen for TLS 1.3, Signal, Noise, WireGuard, JWE, the IETF QUIC handshake, and most modern cryptographic protocols. It is not appropriate for low-entropy inputs such as passwords — use Argon2id, scrypt, or bcrypt for those — and it is not itself a MAC; the underlying HMAC is.
● Beispiele
- 01
TLS 1.3 derives application and exporter traffic keys from the master secret via HKDF-Expand-Label, with separate info contexts per direction.
- 02
A protocol derives a 32-byte encryption key and a 32-byte MAC key from a single DH shared secret by calling HKDF with `info="enc-key"` and `info="mac-key"`.
● Häufige Fragen
Was ist HKDF (HMAC-based Key Derivation Function)?
An extract-then-expand key derivation function based on HMAC, specified in RFC 5869, designed to turn high-entropy but non-uniform secret material (DH shared secrets, master keys) into multiple cryptographically strong keys. Es gehört zur Kategorie Kryptografie der Cybersicherheit.
Was bedeutet HKDF (HMAC-based Key Derivation Function)?
An extract-then-expand key derivation function based on HMAC, specified in RFC 5869, designed to turn high-entropy but non-uniform secret material (DH shared secrets, master keys) into multiple cryptographically strong keys.
Wie funktioniert HKDF (HMAC-based Key Derivation Function)?
HKDF (HMAC-based Key Derivation Function), defined by Krawczyk in RFC 5869 (2010), is the default modern KDF for symmetric key derivation from already-high-entropy inputs such as Diffie-Hellman shared secrets, master keys, or pre-shared keys. It is built in two phases. Extract takes input keying material (IKM) and an optional salt and applies HMAC to produce a fixed-length pseudorandom key (PRK). Expand then applies HMAC iteratively, with a counter and an info-context parameter, to derive output keying material of arbitrary length. The info parameter is used to bind derived keys to a context, which makes it safe to derive many independent keys from one PRK without collision. HKDF is the KDF chosen for TLS 1.3, Signal, Noise, WireGuard, JWE, the IETF QUIC handshake, and most modern cryptographic protocols. It is not appropriate for low-entropy inputs such as passwords — use Argon2id, scrypt, or bcrypt for those — and it is not itself a MAC; the underlying HMAC is.
Wie schützt man sich gegen HKDF (HMAC-based Key Derivation Function)?
Schutzmaßnahmen gegen HKDF (HMAC-based Key Derivation Function) kombinieren typischerweise technische Kontrollen und operative Praktiken, wie in der Definition oben beschrieben.
Welche anderen Bezeichnungen gibt es für HKDF (HMAC-based Key Derivation Function)?
Übliche alternative Bezeichnungen: RFC 5869, HMAC KDF.
● Verwandte Begriffe
- cryptography№ 656
Schlüsselableitungsfunktion (KDF)
Kryptografische Funktion, die aus einem Geheimnis (Passwort, gemeinsam vereinbarter Schlüssel oder Masterschlüssel) einen oder mehrere starke Kryptoschlüssel ableitet.
- cryptography№ 533
HMAC
Mit Schlüssel arbeitende MAC-Konstruktion auf Basis einer kryptografischen Hashfunktion, definiert in RFC 2104 und FIPS 198-1.
- cryptography№ 900
PBKDF2
Passwortbasierte Schlüsselableitungsfunktion gemäß PKCS #5 / RFC 8018, die eine pseudozufällige Funktion mit konfigurierbarer Iterationszahl und Salt iterativ anwendet.
- cryptography№ 068
Argon2
Moderne speicherharte Passwort-Hash- und Schlüsselableitungsfunktion, Sieger der Password Hashing Competition 2015 und in RFC 9106 spezifiziert.
- network-security№ 1279
TLS (Transport Layer Security)
Das von der IETF standardisierte Kryptoprotokoll, das Vertraulichkeit, Integrität und Authentizität für den Verkehr zwischen zwei Netzwerkanwendungen liefert.
- cryptography№ 352
Diffie–Hellman-Schlüsselaustausch
Public-Key-Protokoll, mit dem zwei Parteien über einen unsicheren Kanal ein gemeinsames Geheimnis ableiten, ohne es zu übertragen – beruht auf der Schwierigkeit des diskreten Logarithmus.