@misc{cryptoeprint:2004:365,
author = {Steven D. Galbraith, and J. McKee and P. Valenca},
title = {Ordinary abelian varieties having small embedding degree},
howpublished = {Cryptology ePrint Archive, Report 2004/365},
year = {2004},
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.