Authentication Through Error Estimation in QKD

The one-time pad is an encryption technique that is proven to be unbreakable by an eavesdropper. It relies on a single-use secret key shared between a sender and a receiver, whose length is that of the message to be encrypted. The creation of such a key can be achieved through Quantum Key Distribution (QKD), a method based on quantum physics that ensures eavesdroppers' actions can be statistically detected with arbitrarily high probability. It requires a quantum channel for qubit transmission and a classical channel for classical bit transmission. However, the classical channel is generally authenticated by classical means using cryptographic hash functions that are not provably secure. In this paper, we propose for the first time a QKD protocol, based on BB84, that uses quantum error estimation to authenticate both channels. This method relies on the consumption of a smaller pre-shared key, and is provably secure thanks to fundamental results in both information theory and quantum physics.