HKDF

Table of Contents

• Theory
• Module Methods

Theory

HKDF (RFC 5869) is a simple key derivation function based on HMAC. It is often used to derive multiple session keys from a single master secret.

It follows a standard "Extract-then-Expand" paradigm:

1. Extract: Derives a fixed-length pseudorandom key ($PRK$) from the input keying material ($IKM$) and optional salt.
2. Expand: Expands the $PRK$ into multiple cryptographically strong output keys.

Module Methods

hkdfSync(digest, key, salt, info, keylen)

Synchronous HKDF derivation.

import QuickCrypto from 'react-native-quick-crypto';

// Combined Extract + Expand
const derived = QuickCrypto.hkdfSync(
  'sha256',       // Digest
  'ikm-secret',   // Input Key Material
  'salt',         // Salt
  'context-info', // Context Info
  64              // Output length
);

hkdf(digest, key, salt, info, keylen, callback)