cryptography on computers isolated from open networks
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qrypt0 is a system to exchange messages encrypted by a computer which is permanently offline. The ciphertext is transferred to an online device by representing it as a QR code and scanning it off the screen.

This system provides an effective defence against one of the most common attacks on secure communication: the circumvention of encryption. A typical attack uses computer network exploitation to install malware on the encrypting computer. The malware program then exfiltrates the plaintext to the attacker before encryption is applied.

We still do not have at our disposal operating systems which can be secured effectively against remote injection of malware. Although it requires every user to keep an additional computer offline and physically secure, qrypt0 offers a way to exchange encrypted messages which cannot be compromised by vulnerabilities in the encrypting computer's operating system.