KDF
Key derivation function
A function that derives one or more cryptographic keys from a secret input such as a shared secret, a master key or a password. Key-based KDFs such as HKDF expand an already strong secret; password-based KDFs such as PBKDF2, scrypt and Argon2 are deliberately slow to resist guessing.
- Defined in
- NIST glossary: Key-derivation function
Covered in
Password storage: hashing parameters and rehash on login
Choose Argon2id, scrypt, PBKDF2 or bcrypt with current minimum parameters, store a versioned hash, and upgrade old hashes after a successful login without overwriting a reset.
Choose cryptographic algorithms and parameters by job
A sourced quick reference for October 2026: which algorithm and parameters to use for encryption, hashing, passwords, MACs, signatures, key agreement, key derivation, randomness and TLS, the matching APIs in Node.js, Python, Java, Go and .NET, and where post-quantum migration stands.
Case study: the LastPass breach (2022)
How an attacker went from a compromised developer laptop to a DevOps engineer's home computer, the keys to LastPass's cloud backups and a copy of customer vaults; why each vault's safety then rested on its master password and PBKDF2 iteration count; and what it teaches about backup keys, privileged endpoints, KDF upgrades and unencrypted metadata.
Practice: Insecure randomness lab: Generate unguessable API keys · Password hashing lab: Verify and upgrade an Argon2 password hash on login