@misc{cryptoeprint:2005:013,
author = {Hung-Yu Chien},
title = {Comments: Insider attack on Cheng et al.'s pairing-based tripartite key agreement protocols},
howpublished = {Cryptology ePrint Archive, Report 2005/013},
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.