@misc{cryptoeprint:2007:035,
author = {Louis Goubin and Jean-Michel Masereel and Michael Quisquater},
title = {Cryptanalysis of white box DES implementations},
howpublished = {Cryptology ePrint Archive, Report 2007/035},
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.