For local backups, Apple says [1] that "There is no way to recover your information or turn off Encrypt Backup if you lose or forget the password." so I'm incli

For local backups, Apple says [1] that "There is no way to recover your information or turn off Encrypt Backup if you lose or forget the password." so I'm inclined to thinking it's done with a secure symmetric encryption scheme with the key held by the user. If that's the case, since iTunes prompts you for a separate backup password (only used when restoring a backup), a security-conscious user would probably make that password sufficiently long as to be impossible to brute-force, regardless of any help from Apple. [1]: https://support.apple.com/en-us/HT205220 https://support.apple.com/en-us/HT205220