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 key derivation algorithm defined in RFC 5869. It allows you to take a shared secret (input key material) and derive multiple strong, cryptographically independent keys from it.
HKDF works in two stages: an "extract" stage that uses HMAC with a salt to produce a pseudorandom key, and an "expand" stage that uses the pseudorandom key with application-specific info to generate one or more derived keys.
HKDF is widely used in TLS, secure messaging, and cryptographic APIs where one shared secret must be expanded into multiple cryptographic keys for different purposes (encryption, authentication, etc).