Defeating Man-in-the-Middle Attack in Quantum Key Distribution

Quantum cryptosystems use some properties of quantum mechanics to create secret shared cryptographic keys that remain secret even against an eavesdropper with an access to unlimited computational power. All quantum key distribution (QKD) protocols require that the parties have access to an authentic channel. Otherwise, QKD is vulnerable to man-in-the-middle attacks. This paper studies QKD from this point of view, emphasizing the necessity and sufficiency of using unconditionally secure authentication in quantum cryptosystems. In this work, a new technique of using unconditionally secure authentication is proposed for quantum cryptosystems. This technique is based on a hybrid of normal application of authentication codes and the so-called “counterbased” authentication method such that to achieve a better trade off between security and efficiency (in terms of the required size of initially shared secret data). Based on this strategy, an authenticated version of a typical QKD protocol (the well-known BB84 protocol) is described.