A Review on Continuous-Variable Quantum Key Distribution Security

Regarding the security concerns arising from the threat that quantum computing algorithms pose on some today’s most efficient and widely implemented public-key cryptographic systems, it has become necessary to find alternative cryptographic techniques to support private (or symmetric) key cryptographic schemes by means of key distribution. In this article we survey the emerging technology of quantum key distribution (QKD), which enables two separate parties to distill a random secret key only known by them and whose security relies on the principles of quantum physics, with the advantage of also enabling the detection of potential eavesdroppers. Among the different existing approaches to QKD, a distinction is made between discrete and continuous variable protocols. We focus here on continuous variable (CV-QKD) protocols, which consist of encoding information in optical coherent states that can be transmitted by fiber by means of off-the-shelf devices widely used in today’s telecommunications industry. An important advantage is that these components have a significantly lower cost in comparison to those used in other QKD protocols. The present study highlights some information-theoretic aspects of CV-QKD while putting special efforts into the security analysis of these protocols (such as parameter estimation or error correction techniques) derived from the practical implementation, as well as the challenges this technology faces in its still ongoing development.