@misc{cryptoeprint:2009:490,
author = {Sang-Gon Lee},
title = {Cryptanalysis of Multiple-Server Password-Authenticated Key},
howpublished = {Cryptology ePrint Archive, Report 2009/490},
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.