@misc{cryptoeprint:2011:590,
author = {Jianwei Li and Yanbin Pan and Mingjie Liu and Guizhen Zhu},
title = {An Efficient Broadcast Attack against NTRU},
howpublished = {Cryptology ePrint Archive, Report 2011/590},
year = {2011},
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.