@misc{cryptoeprint:2006:200,
author = {Guanfei Fang and Genxun huang},
title = {Improvement of recently proposed Remote User Authentication Schemes},
howpublished = {Cryptology ePrint Archive, Report 2006/200},
year = {2006},
note = {\url{http://eprint.iacr.org/}},
}
You will need the url.sty package (comes with most LaTeX installations) for the last line. Otherwise, remove the \url command.