@misc{cryptoeprint:2014:899,
author = {Colin O'Flynn and Zhizhang Chen},
title = {Side Channel Power Analysis of an AES-256 Bootloader},
howpublished = {Cryptology ePrint Archive, Report 2014/899},
year = {2014},
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.