Secret keys agreement in communication networks with quantum key distribution and trusted nodes

Abstract

Basic configuration in quantum cryptography is a point-to-point quantum key distribution. In networks with quantum key distribution, the keys received on different network segments are different. For information encryption between arbitrary network nodes it is necessary to have agreement of the keys distributed in different segments of network through a public classical communication channel. The secrecy criterion for keys independently distributed in different network segments is formulated in terms of the trace distance. These are the so-called ε–secret keys. The paper deals with the issue of the secrecy of the agreed keys. We propose the method of secret keys agreement in which the agreement of two ε1, ε2–secret keys distributed in different segments leads to a common –secret key. It is shown that in order to agreed common key will be ε–secret, it is sufficient that the keys on the individual segments are ε/2–secret.