[ecolonsmak]

Is there a way to use this method to stash a crypto key inside the file that could be used to authenticate a nft against a Blockchain?

[TeMPOraL]

Yes, but then the key can also be trivially removed, leaving you with the same image, sans the key.

Artificial digital scarcity and general-purpose computers don't mix.

(Which is why we've been fighting and losing the war on the latter for a good decade now.)