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Vol. 1 · Ed. 2026
CyberGlossary
Русский
Entry № 532

HKDF (HMAC-based Key Derivation Function)

Что такое 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.

● Примеры

  1. 01

    TLS 1.3 derives application and exporter traffic keys from the master secret via HKDF-Expand-Label, with separate info contexts per direction.

  2. 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"`.

● Частые вопросы

Что такое 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. Относится к категории Криптография в кибербезопасности.

Что означает 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.

Как работает 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.

Как защититься от HKDF (HMAC-based Key Derivation Function)?

Защита от HKDF (HMAC-based Key Derivation Function) обычно сочетает технические меры и операционные практики, как описано в определении выше.

Какие есть другие названия HKDF (HMAC-based Key Derivation Function)?

Распространённые альтернативные названия: RFC 5869, HMAC KDF.

● Связанные термины