@misc{cryptoeprint:2006:199,
author = {L. Chen and Z. Cheng and N.P. Smart},
title = {Identity-based Key Agreement Protocols From Pairings},
howpublished = {Cryptology ePrint Archive, Report 2006/199},
year = {2006},
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.