The PoW is the number of leading zeros in the ID, so maybe not. Pow could be done, then signing could be done on device. Yeah, I guess that tracks.
Discussion
Yeah, PoW can be built into the binary version of the npub (no nonce), or into a hash of any values. To prove we aren’t just reusing an old PoW i guess it should be a hash of the contents of the signed message. The PoW verification would work nicely into the signature verification flow.