keying

Keying is a term used in several fields to describe the use or creation of a key that unlocks or enables a process. In each context, keying denotes a defined relationship between a key material and the system it governs, such as a lock, a color, or a cryptographic secret.

In physical security, keying refers to configuring locks and cylinders to operate with a specific key or set of keys. Common arrangements include keyed-alike systems, where multiple locks share a single key; master keying, which establishes a hierarchy of keys that can open multiple locks; and rekeying, the process of replacing the working keys so old keys no longer fit. Keying involves determining key cuts (bitting) and maintaining records to manage access rights and key control.

In film, television, and digital video, keying describes chroma keying and related techniques used to separate a foreground subject from a colored background. The process often uses a green or blue screen to create a matte, which is then replaced with a different image or video. Keying involves color sampling, matte extraction, spill suppression, and edge refinement to produce a clean composite.

In cryptography and information security, keying refers to the creation, distribution, and management of cryptographic keys used to encrypt and decrypt data. This includes key generation, exchange, derivation, storage, rotation, and revocation, typically managed by dedicated key management systems to maintain confidentiality and integrity.

Keying can thus refer to configuring access, isolating signals, or securing information, depending on the domain. See-also terms include keyed alike, master keying, chroma keying, and key exchange.