If CF download the file to check the hash, it wouldn't really be helpful as a caching service. That would mean CF would hit your server for each request before

If CF download the file to check the hash, it wouldn't really be helpful as a caching service. That would mean CF would hit your server for each request before it served up the asset to the customer. Your server wouldn't benefit from caching. Maybe you'd get a small speed increase from their worldwide endpoints but that would reduce the advantage of having CF manage your site. One of the biggest advantages is that CF serves hits that your server wouldn't have to. That allows you to need less infrastructure. Further, it might be better to never serve sensitive financial data via a 3rd party server. That kind of data would be best served directly to the customer's browser from your server.