@misc{cryptoeprint:2008:098,
author = {Xu-An Wang and Xiaoyuan Yang and Yiliang Han},
title = {On Security Notions for Verifiable Encrypted Signature},
howpublished = {Cryptology ePrint Archive, Report 2008/098},
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.