@misc{cryptoeprint:2010:113,
author = {Xu An Wang and Xiaoyuan Yang},
title = {Cryptanalysis of Two Efficient HIBE Schemes in the Standard Model},
howpublished = {Cryptology ePrint Archive, Report 2010/113},
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.