@misc{cryptoeprint:2014:770,
author = {Takaaki Mizuki and Yu-ichi Hayashi},
title = {AES Cipher Keys Suitable for Efficient Side-Channel Vulnerability Evaluation},
howpublished = {Cryptology ePrint Archive, Report 2014/770},
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.