The password and ID management system in the Mac, iPhone and iPad. In the late 1990s, Apple introduced Keychain (not iCloud Keychain) for the Mac to keep track of logins for various accounts. Storing data locally, Keychain was later enhanced to include encryption keys and digital certificates.
iCloud Keychain
In 2011, Apple introduced iCloud, and iCloud Keychain data are stored on Apple's servers, enabling access from a Mac, iPhone or iPad. Mac users who also work on PCs can use iCloud for Windows to make the data available on Windows. See
iCloud.