Apple Inc.
File system support for rolling keys on file extents

Abstract:

This application sets forth a key rolling technique for a file system of a computing device. The key rolling technique allows for files to be transparently re-encrypted in a background process while still allowing applications to access the files being re-encrypted. During re-encryption, at least one file extent of a file is decrypted using a current key for the file extent and re-encrypted using a new key for the file extent. Moreover, the file extent can be relocated to another location in memory during re-encryption to enhance accessibility and crash protection features. Metadata associated with the file can be updated to include information pertaining to both the location of the re-encrypted file extent as well as the new key that can be used to decrypt the re-encrypted file extent. In this manner, the metadata can be used to properly construct a complete file when the file needs to be accessed.