@misc{cryptoeprint:2008:105,
author = {W. Michiels and P. Gorissen and H.D.L. Hollmann},
title = {Cryptanalysis of White-Box Implementations},
howpublished = {Cryptology ePrint Archive, Report 2008/105},
year = {2008},
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.