Would it be possible for an application to encrypt a file against a public address and send that to someone to open with their private key? Private key then acting as proof of person, to the extent required. Is there already a standalone application that can do that with Bitcoin addresses and private keys?
I wondered that one step beyond that might lend itself to PeerTracks but then I'm one of many that hates DRM, so perhaps that's not where PeerTracks will want to go.