@misc{cryptoeprint:2015:814,
author = {Qingji Zheng and Xiangxue Li and Aytac Azgin},
title = {CLKS: Certificateless Keyword Search on Encrypted Data},
howpublished = {Cryptology ePrint Archive, Report 2015/814},
year = {2015},
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.