Comment on “Quantum key distribution without alternative measurements” [Phys. Rev. A 61 , 052312 (2000)]

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.