@misc{cryptoeprint:2015:533,
author = {Xiaoshuang Ma and Kexin Qiao},
title = {Related-Key Rectangle Attack on Round-reduced \textit{Khudra} Block Cipher},
howpublished = {Cryptology ePrint Archive, Report 2015/533},
year = {2015},
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.