But in the documentation[1] under the heading "Encryption of certain metadata and usage information" they state:
> Some metadata and usage information stored in iCloud remains under standard data protection, even when Advanced Data Protection is enabled. For example, dates and times when a file or object was modified are used to sort your information, and checksums of file and photo data are used to help Apple de-duplicate and optimize your iCloud and device storage
This checksum is described as:
> The raw byte checksum of the photo or video
This hash can technically be shared by Apple, since they own the key used to encrypt it. And depending on when the hash is computed (post-encryption it's no problem, pre-encryption we have a problem), this could technically be used to find people sharing known undesired images e.g. Tank Man or CSAM.
> Some metadata and usage information stored in iCloud remains under standard data protection, even when Advanced Data Protection is enabled. For example, dates and times when a file or object was modified are used to sort your information, and checksums of file and photo data are used to help Apple de-duplicate and optimize your iCloud and device storage
This checksum is described as:
> The raw byte checksum of the photo or video
This hash can technically be shared by Apple, since they own the key used to encrypt it. And depending on when the hash is computed (post-encryption it's no problem, pre-encryption we have a problem), this could technically be used to find people sharing known undesired images e.g. Tank Man or CSAM.
[1]: https://support.apple.com/en-us/HT202303#advanced