@misc{cryptoeprint:2006:248,
author = {Steven D. Galbraith},
title = {Disguising tori and elliptic curves},
howpublished = {Cryptology ePrint Archive, Report 2006/248},
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.