@misc{cryptoeprint:2010:211,
author = {Keting Jia and Jiazhe Chen and Meiqin Wang and Xiaoyun Wang},
title = {Practical-time Attack on the Full MMB Block Cipher},
howpublished = {Cryptology ePrint Archive, Report 2010/211},
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.