The keychain database is encrypted per-table and per-row with AES-256-GCM. The command line equivalent of Keychain Access is /usr/bin/security. It is free, open source software released under the terms of the APSL-2.0. In macOS, keychain files are stored in ~/Library/Keychains/ (and subdirectories), /Library/Keychains/, and /Network/Library/Keychains/, and the Keychain Access GUI application is located in the Utilities folder in the Applications folder. A Keychain can contain various types of data: passwords (for websites, FTP servers, SSH accounts, network shares, wireless networks, groupware applications, encrypted disk images), private keys, certificates, and secure notes.
It was introduced with Mac OS 8.6, and has been included in all subsequent versions of the operating system, now known as macOS. Keychain is the password management system in macOS, developed by Apple.
