HKDF Generator (HMAC-based Key Derivation Function)
HKDF FAQ
What is HKDF used for?
HKDF is used to derive multiple strong cryptographic keys from a single shared secret, ensuring key separation for encryption, authentication, and other purposes.
Why is salt important in HKDF?
Salt adds randomness to the key derivation process. While optional, it is highly recommended for stronger security.
What is the role of 'info' in HKDF?
The 'info' parameter allows domain separation. It ensures derived keys are unique to a specific application or usage context.
Which hash function should I use?
SHA-256 is widely used and considered secure. For stronger security or larger output sizes, SHA-512, SHA3-256, or BLAKE2 variants can be chosen.
Is HKDF secure?
Yes. HKDF is proven secure as long as the underlying HMAC and hash function are secure.
What is HKDF?
HKDF (HMAC-based Key Derivation Function) is a standardized algorithm defined in RFC 5869. It takes an initial secret (IKM) and derives multiple strong, independent cryptographic keys from it. Unlike simpler schemes, HKDF separates randomness extraction from expansion, making it robust across a variety of cryptographic contexts.
How It Works
HKDF operates in two main stages:
- Extract: The input key material is combined with an optional salt using HMAC to produce a pseudorandom key.
- Expand: The pseudorandom key is expanded with application-specific
infovalues to derive one or more cryptographically strong subkeys.
Common Uses
HKDF is widely deployed in protocols like TLS 1.3, Signal, and IPsec. It’s often compared to other derivation functions such as PBKDF2 and Argon2.
Why Use Salt and Info?
- Salt: Randomizes the derivation process, protecting against rainbow table attacks. For random salts, see our Salt Generator.
- Info: Provides domain separation, ensuring derived keys are tied to a specific protocol, application, or purpose.
HKDF vs Other Tools
| Algorithm | Main Use | Strength |
|---|---|---|
| PBKDF2 | Password hashing & key stretching | Secure, but older |
| Argon2 | Modern password hashing (memory-hard) | Highly secure |
| HKDF | Deriving multiple keys from a single shared secret | Secure when paired with strong HMAC |
About This Tool
This free HKDF Generator runs entirely in your browser. All operations are 100% client-side, similar to our Hex ↔ UTF-8 ↔ Base64 Converter and JWT Decoder. No data is ever sent to a server, ensuring complete privacy.