@misc{cryptoeprint:2006:161,
author = {Zhangyi Wang and Huanguo Zhang and Zhongping Qin and Qingshu Meng},
title = {Cryptanalysis of 4-Pass HAVAL},
howpublished = {Cryptology ePrint Archive, Report 2006/161},
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.