@misc{cryptoeprint:2013:071,
author = {Jérémie Detrey and Pierrick Gaudry and Marion Videau},
title = {Relation collection for the Function Field Sieve},
howpublished = {Cryptology ePrint Archive, Report 2013/071},
year = {2013},
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.