@misc{cryptoeprint:2015:218,
author = {wang qinglong},
title = {Efficient k-out-of-n oblivious transfer protocol},
howpublished = {Cryptology ePrint Archive, Report 2015/218},
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.