@misc{cryptoeprint:2009:143,
author = {Soyoung Park and Sang-Ho Lee and Joohan Lee},
title = {Multiple and Unlinkable Public Key Encryption without Certificates},
howpublished = {Cryptology ePrint Archive, Report 2009/143},
year = {2009},
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.