@misc{cryptoeprint:2005:209,
author = {Jin Wook Byun and Dong Hoon Lee},
title = {Comments on Weaknesses in Two Group Diffie-Hellman Key Exchange Protocols},
howpublished = {Cryptology ePrint Archive, Report 2005/209},
year = {2005},
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.