@misc{cryptoeprint:2014:065,
author = {Palash Sarkar and Shashank Singh},
title = {Fine Tuning the Function Field Sieve Algorithm for the Medium Prime Case},
howpublished = {Cryptology ePrint Archive, Report 2014/065},
year = {2014},
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.