@misc{cryptoeprint:2011:364,
author = {Jean-Pierre Flori and Sihem Mesnager and Gérard Cohen},
title = {The Value $4$ of Binary Kloosterman Sums},
howpublished = {Cryptology ePrint Archive, Report 2011/364},
year = {2011},
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.