Security analysis and improvements of two QKD protrocols using complete Bell-state measurements

Security analysis for two quantum key distribution protocols was presented by using EPR pair and complete Bell-state measurements. It is also shown that those two protocols are totally equivalent from the point of view of the topological structures on how to measure the corresponding qubits at random. The paper proved that Bell-state measurement basis can detect some special eavesdropping behaviors, but not all of them. Thus, this enables all same errors occurring on the sampling qubits undetected, which impairs the security of quantum key distribution protocols. |0 + >, |0->, |1 + >, |1-> measurement basis was used to replace complete Bell-state basis, which can avoid the incomplete error-detecting strategy. And unconditionally security was guaranteed by the improved protocol.