@misc{cryptoeprint:2009:437,
author = {Shengbao Wang},
title = {On the Relations Between Diffie-Hellman and ID-Based Key Agreement from Pairings},
howpublished = {Cryptology ePrint Archive, Report 2009/437},
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.