@misc{cryptoeprint:2010:322,
author = {Orr Dunkelman and Nathan Keller and Adi Shamir},
title = {Improved Single-Key Attacks on 8-round AES},
howpublished = {Cryptology ePrint Archive, Report 2010/322},
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.