@misc{cryptoeprint:2009:561,
author = {Yalin Chen1, Jue-Sam Chou2,* , Chun-Hui Huang3},
title = {Improvements on two password-based authentication protocols},
howpublished = {Cryptology ePrint Archive, Report 2009/561},
year = {2009},
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.