Why is Advanced Data Protection not supported?

[neilschark]

Unfortunately, ADP is not supported. The docs say

ADP
Advanced Data Protection (ADP) for iCloud accounts is not supported because icloudpd simulates web access, which is disabled with ADP.

But the stated reason is not true. You can use iCloud-Web with ADP, your Keys get on the fly send from one of your devices to the servers to encrypt the data once.

It may be a problem for autoamted syncing the data every night or something, but for manually triggering a download/sync it should not be a problem.

[AndreyNikiforov]

I don't have ADP enabled and haven't experimented with it. From what I am reading about it, web access can be enabled for short period of time (1hr?). It is unclear if that can be enabled from icloudpd code or has to be enabled through icloud.com. The limitation of 1hr makes this feature not of high interest and complication with implementation reduces value further. I suspect that a good research/analysis/experimentation may change the balance.