@misc{cryptoeprint:2011:569,
author = {Ming Li, Ali Miri and Daming Zhu},
title = {Analysis of the Hamming Weight of the Extended wmbNAF},
howpublished = {Cryptology ePrint Archive, Report 2011/569},
year = {2011},
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.