A Key Derivation Function (KDF) is a cryptographic algorithm designed to transform a secret value, such as a password or passphrase, into a secure cryptographic key. KDFs are essential in scenarios where human-memorable passwords need to be converted into strong, random-like keys suitable for encryption, authentication, or digital signatures. They often use techniques like salting and multiple iterations to resist brute-force and dictionary attacks, making it significantly harder for attackers to guess the original password. Common KDFs include PBKDF2, bcrypt, and scrypt. By using a KDF, systems enhance the security of stored credentials and encrypted data.