@misc{cryptoeprint:2014:368,
author = {Erich Wenger and Paul Wolfger},
title = {Solving the Discrete Logarithm of a 113-bit Koblitz Curve with an FPGA Cluster},
howpublished = {Cryptology ePrint Archive, Report 2014/368},
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.