@misc{cryptoeprint:2015:888,
author = {Kazuhiko Minematsu and Tetsu Iwata},
title = {Tweak-Length Extension for Tweakable Blockciphers},
howpublished = {Cryptology ePrint Archive, Report 2015/888},
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.