@misc{cryptoeprint:2006:138,
author = {Onur Ac\i{}i\c{c}mez and \c{C}etin Kaya Ko\c{c}},
title = {Trace-Driven Cache Attacks on AES},
howpublished = {Cryptology ePrint Archive, Report 2006/138},
year = {2006},
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.