@misc{cryptoeprint:2010:172,
author = {Qixiang Mei， Bao Li，Xianhui Lu and Dingding Jia},
title = {Chosen Ciphertext Secure Encryption over Semi-smooth Subgroup},
howpublished = {Cryptology ePrint Archive, Report 2010/172},
year = {2010},
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.