Security

iCloud overview

iCloud stores a user’s contacts, calendars, photos, documents, and more, and keeps the information up to date across all of their devices, automatically. iCloud can also be used by third-party apps to store and sync documents, as well as key values for app data as defined by the developer. Users set up iCloud by signing in with an Apple ID and choosing which services they would like to use. Certain iCloud features, iCloud Drive, and iCloud Backup can be disabled by IT administrators using mobile device management (MDM) configuration profiles. The service is agnostic about what is being stored and handles all file content the same way, as a collection of bytes.

Each file is broken into chunks and encrypted by iCloud using AES-128 and a key derived from each chunk’s contents, with the keys using SHA-256. The keys and the file’s metadata are stored by Apple in the user’s iCloud account. The encrypted chunks of the file are stored, without any user-identifying information or the keys, using both Apple and third-party storage services—such as Amazon Web Services or Google Cloud Platform—but these partners don’t have the keys to decrypt the user’s data stored on their servers.

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Apple Platform Security

iCloud overview