@misc{cryptoeprint:2010:661,
author = {Ruilin Li and Chao Li and Jinshu Su and Bing Sun},
title = {Security Evaluation of MISTY Structure with SPN Round Function},
howpublished = {Cryptology ePrint Archive, Report 2010/661},
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.