Kevin, an encryption specialist, implemented a technique that enhances the security of keys used for encryption and authentication. Using this technique, Kevin input an initial key to an algorithm tha

A Key Derivation Function (KDF) is a specific algorithm used *within* the key stretching process to generate a cryptographic key from a secret, such as a master key or password, but key stretching is the broader *technique* focused on making the key resistant to brute-force attacks through iterative computation.

Key reinstallation is a vulnerability (e.g., KRACK attack on WPA2) where an attacker forces the reinstallation of a cryptographic key already in use, allowing for replay or decryption, which is a security flaw, not an enhancement technique.

A Public Key Infrastructure (PKI) is a system for managing digital certificates and public keys, establishing trust for secure communication, but it is not a technique for strengthening a single encryption key against brute-force attacks.

Key stretching is a cryptographic technique that intentionally makes a password or key computationally expensive to derive from its initial input by applying an iterative process, often involving a Key Derivation Function (KDF) and salt. This increased cost significantly slows down brute-force attacks, making it impractical for attackers to guess or crack the strengthened key within a reasonable timeframe.