@misc{cryptoeprint:2011:627,
author = {Sihem Mesnager},
title = {A note on semi-bent functions with multiple trace terms and hyperelliptic curves},
howpublished = {Cryptology ePrint Archive, Report 2011/627},
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.