@misc{cryptoeprint:2008:200,
author = {J. Wu and D.R. Stinson},
title = {On The Security of The ElGamal Encryption Scheme and Damgard’s Variant},
howpublished = {Cryptology ePrint Archive, Report 2008/200},
year = {2008},
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.