  A system is described for exchanging encrypted short messages between
computers which remain permanently isolated from any network accessible to the
attacker. The main advantage is effective protection of these computers from
malware which could circumvent the encryption. For transmission, the ciphertext
is passed between isolated and connected computers in the form of a QR code,
which is displayed on and scanned from a screen. The security of qrypt0
therefore rests on the cryptography and the computer's physical isolation
rather than on the computer security of the encrypting device.
