keys

Keys is a term with several senses. In the common use, a key is a device that opens a lock, usually made of metal or plastic. The word also appears in music, computing, and geography to denote access, organization, or information.

Physical keys are metal or plastic implements that, when cut to match a specific lock, can retract pins or actuate levers to release the mechanism. They are defined by cuts, bittings, and profiles, determining which pins align. Master keys and skeleton keys open multiple locks; duplication and control are central to security.

In computing and information security, a key is information used to control cryptographic operations. Symmetric keys are shared to encrypt and decrypt data, while asymmetric systems use a public key for encryption and a private key for decryption or signing. Key length, entropy, and secure management—generation, storage, rotation, and revocation—are central concerns. In user systems, API keys or SSH keys serve as credentials for authenticating applications and users.

In music, a key designates the tonal center and scale of a composition, usually shown by a key signature and major or minor mode. In cartography, a map key or legend explains symbols and colors and may include scale information. The term is also used in data visualization to describe mappings from data to visuals.

The Florida Keys are a chain of tropical islands off the southern coast of Florida, extending into the Gulf of Mexico and the Atlantic Ocean. The region includes cultural and ecological sites and is connected by the Overseas Highway.