@misc{cryptoeprint:2014:704,
author = {Shenghui Su and Shuwang Lü and Daqiang Dong},
title = {A 128-bit Block Cipher Based on Three Group Arithmetics},
howpublished = {Cryptology ePrint Archive, Report 2014/704},
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.