@misc{cryptoeprint:2004:118,
author = {Stéphane Flon and Roger Oyono and Christophe Ritzenthaler },
title = {Fast addition on non-hyperelliptic genus $3$ curves
},
howpublished = {Cryptology ePrint Archive, Report 2004/118},
year = {2004},
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.