@misc{cryptoeprint:2010:400,
author = {Kitae Kim and Dahun Nyang},
title = {Security Analysis of a Threshold Proxy Signature Scheme},
howpublished = {Cryptology ePrint Archive, Report 2010/400},
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.