@misc{cryptoeprint:2015:874,
author = {Yuanxi Dai and John Steinberger},
title = {Feistel Networks: Indifferentiability at 10 Rounds},
howpublished = {Cryptology ePrint Archive, Report 2015/874},
year = {2015},
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.