Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Keychain is Apple Inc.'s password management system in Mac OS. It was introduced with Mac OS 8.6, and has been included in all subsequent versions of Mac OS, including Mac OS X. A Keychain can contain various types of data: passwords (Websites, FTP servers, SSH accounts, network shares, wireless networks, groupware applications, encrypted disk images), private keys.