Key generation schemes for channel authentication in quantum key distribution protocol

Quantum key distribution (QKD) systems enable secure key generation between two parties. Such systems require an authenticated classical channel for QKD protocols to work. Usually, the initial authentication key for this channel is pre-shared. In this work, methods that are used to renew the pre-shared keys ensuring a high level of security and performance for the subsequent quantum key generation are discussed. The model of QKD systems in terms of the lifecycle of the keys is formalised and a full set of parameters that can be used for key renewal functions is described. A detailed adversary model allows us to compare key renewal schemes by the probabilities of successful attacks and their consequences. As a result, it is shown that a hybrid key renewal scheme, which uses both the auxiliary pre-shared key and a part of the quantum sequence, has the higher security properties among considered schemes and is recommended to be used in QKD systems.