@misc{cryptoeprint:2007:442,
author = {Neal Koblitz and Alfred Menezes},
title = {Another Look at Non-Standard Discrete Log and Diffie-Hellman Problems},
howpublished = {Cryptology ePrint Archive, Report 2007/442},
year = {2007},
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.