@misc{cryptoeprint:2011:478,
author = {Debiao He, Sahadeo Padhye, Jianhua Chen},
title = {An efficient certificateless authenticated key agreement scheme},
howpublished = {Cryptology ePrint Archive, Report 2011/478},
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.