We show that the revised KKKP protocol proposed by Kye and Kim [Phys. Rev. Lett. 95,040501(2005)] is still insecure with coherent states by a type of beamsplitting attack. We then further revise the KKKP protocol so that it is secure under such type of beamsplitting attack. The revised scheme can be used for not-so-weak coherent state quantum key distribution.
@article{arxiv.quant-ph/0603010,
title = {Beamsplitting attack to the revised KKKP protocol and a possible solution},
author = {Xiang-Bin Wang and Qiang Zhang and Yu-Ao Chen and Wong-Young Hwang and Myungshik Kim and Jian-Wei Pan},
journal= {arXiv preprint arXiv:quant-ph/0603010},
year = {2007}
}