@misc{cryptoeprint:2010:168,
author = {Xuehai Tang, Bing Sun, Ruilin Li and Chao Li},
title = {A Meet-in-the-Middle Attack on ARIA},
howpublished = {Cryptology ePrint Archive, Report 2010/168},
year = {2010},
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.