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

4-Tosyl-1-oxa-4-aza­spiro­[4.5]deca-6,9-dien-8-one

In the mol­ecule of the title compound, C15H15NO4S, the two six-membered rings are almost parallel to each other [dihedral angle = 1.87 (9)°] and perpendicular to the mean plane through the five-membered ring [dihedral angles of 89.98 (10) and 89.04 (10)°]. The crystal structure is stabilized by inter­molecular C—H⋯O hydrogen-bonding inter­actions

(Benzoato-κO)bis­(1,10-phenanthroline-κ2 N,N′)copper(II) chloride benzoic acid disolvate

In the title complex, [Cu(C7H5O2)(C12H8N2)2]Cl·2C6H5CO­OH, the CuII ion is coordinated by one carboxyl­ate O atom from a benzoate anion and four N atoms from two phenantroline ligands in a distorted five-coordinate trigonal-bipyramidal CuON4 chromophore. The Cu2+ and the Cl− ion are imposed by a twofold rotation axiss which also bisects the equally disordered benzoate anion. In the crystal, the mol­ecules are assembled into chains along [010] by C—H⋯Cl, O—H⋯Cl and C—H⋯O hydrogen-bonding inter­actions. The resulting chains are further connected into two-dimensional supra­molecular layers parallel to [100] by inter­chain π⋯π stacking inter­actions [centroid–centroid distance = 3.823 (5) Å] between the phenanthroline ligands and the benzoic acid mol­ecules, and by C—H⋯O hydrogen-bonding inter­actions. Strong π⋯π stacking inter­actions between adjacent phenantroline ligands [3.548 (4) Å] assemble the layers into a three-dimensional supra­molecular architecture