@misc{cryptoeprint:2008:508,
author = {Fabrice J.P.R. Pautot},
title = {Some Formal Solutions in Side-channel Cryptanalysis - An Introduction},
howpublished = {Cryptology ePrint Archive, Report 2008/508},
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.