Abstract
Recently, multiparty quantum key agreement (MQKA) protocols have gained increasing attention. Several MQKA protocols in the traveling mode have been proposed for higher key generation rates, which, however, are vulnerable to a collusive attack presented by Liu. In this paper, an analysis of Liu's collusive attacks on Cao et al.'s protocol is given, based on which an efficient MQKA protocol that requires only sequential communication of a single d-level quantum system is put forward. Because of the single d-level quantum system, our protocol has huge advantages in scalability and can be realized with the state-of-the-art technology. The scalability means that each additional participant is only required to perform a unitary operator that is comparatively simple, and the complexity of measurements remains independent of the number of participants. Our protocol can also resist Liu's collusive attacks due to the encrypted quantum channel and has an efficiency rate of 1/2N(N is the number of participants) that is much better than those of other quantum key agreement protocols. In addition, by using the proposed encoding method, a wide class of problems for which quantum information protocols based on multisystem entanglement can be mapped into much simpler ones involving only one system.
Highlights
Quantum key distribution is the best-known example of a quantum cryptographic task which is a secure communication method implementing a cryptographic protocol involving components of quantum mechanics
The quantum channel is encrypted by a unitary operation during the key agreement protocol
We hope the results of the presented paper will be helpful for further research on fair and efficient multiparty quantum key agreement (QKA)
Summary
Quantum key distribution is the best-known example of a quantum cryptographic task which is a secure communication method implementing a cryptographic protocol involving components of quantum mechanics. It was found that most of the quantum key agreement protocols cannot resist collusive attacks [18], i.e., part of the participants of the group can predetermine the shared key before the end of the protocol. Liu’s protocol [18] shows that the collusive attack on quantum multiparty key agreement protocols can succeed in a travelling mode since the dishonest participants share the information of the initial prepared quantum states with each other. A. OUR CONTRIBUTIONS In this paper, a multiparty quantum key agreement protocol against collusive attacks with d-level quantum systems in the travelling mode is presented. PRELIMINARIES In the proposed protocol, all parties choose the quantum state from a measurement basis which belongs to a set of d mutually unbiased (orthonormal) bases (MUBs).
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