Integrating Classical Preprocessing into an Optical Encryption Scheme

Traditionally, cryptographic protocols rely on mathematical assumptions and results to establish security guarantees. Quantum cryptography has demonstrated how physical properties of a communication channel can be leveraged in the design of cryptographic protocols, too. Our starting point is the AlphaEta protocol, which was designed to exploit properties of coherent states of light to transmit data securely over an optical channel. AlphaEta aims to draw security from the uncertainty of any measurement of the transmitted coherent states due to intrinsic quantum noise. We present a technique to combine AlphaEta with classical preprocessing, taking into account error-correction for the optical channel. This enables us to establish strong provable security guarantees. In addition, the type of hybrid encryption we suggest, enables trade-offs between invoking a(n inexpensive) classical communication channel and a (more complex to implement) optical channel, without jeopardizing security. Our design can easily incorporate fast state-of-the-art authenticated encryption, but in this case the security analysis requires heuristic reasoning.