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.
@article{arxiv.quant-ph/0009042,
title = {Comment on "Quantum key distribution without alternative measurements"},
author = {Yong-Sheng Zhang and Chuan-Feng Li and Guang-Can Guo},
journal= {arXiv preprint arXiv:quant-ph/0009042},
year = {2009}
}