Cryptanalysis of a multi-party quantum key agreement protocol with single particles

Recently, Sun et al. [Quant Inf Proc DOI: 10.1007/s11128-013-0569-x] presented an efficient multi-party quantum key agreement (QKA) protocol by employing single particles and unitary operations. The aim of this protocol is to fairly and securely negotiate a secret session key among $N$ parties with a high qubit efficiency. In addition, the authors claimed that no participant can learn anything more than his/her prescribed output in this protocol, i.e., the sub-secret keys of the participants can be kept secret during the protocol. However, here we points out that the sub-secret of a participant in Sun et al.'s protocol can be eavesdropped by the two participants next to him/her. In addition, a certain number of dishonest participants can fully determine the final shared key in this protocol. Finally, we discuss the factors that should be considered when designing a really fair and secure QKA protocol.Comment: 7 page

1-Cyano­methyl-1,4-diazo­niabicyclo­[2.2.2]octane tetra­chloridocuprate(II)

In the crystal structure of the title compound, (C8H15N3)[CuCl4], the cations and anions, in which the CuII atom is tetra­hedrally coordinated, are linked via N—H⋯Cl hydrogen bonds into chains that are elongated in the c-axis direction