@misc{cryptoeprint:2007:450,
author = {Xiaohui Liang and Zhenfu Cao and Jun Shao and Huang Lin },
title = {Short Group Signature without Random Oracles },
howpublished = {Cryptology ePrint Archive, Report 2007/450},
year = {2007},
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.