Comment on "Quantum key distribution without alternative measurements"
  In a recent paper [A. Cabello, Phys. Rev. A 61, 052312 (2000)], a quantum key distribution protocol based on entanglement swapping was proposed. However, in this comment, it is shown that this protocol is insecure if Eve use a special strategy to attack. 
Yong-Sheng Zhang, Chuan-Feng Li, and Guang-Can Guo (University of   Science and Technology of China)