Sibelius has an encrypted file format. Finale recently decided to go this way too.
What will the dorico policy be?
Dorico’s file format is proprietary and we do not plan to document its internals for public consumption, because that would not really be useful to anybody, as Dorico’s project files can only feasibly be read by Dorico.
The files are not really encrypted in any meaningful way: if you really want to, you can poke around inside them by unzipping them with any zip utility (they use the OCF standard as a wrapper for the various things contained in a Dorico project), but you won’t be able to do anything too useful with them if you do.