@misc{cryptoeprint:2015:762,
author = {Riham AlTawy and Ahmed Abdelkhalek and Amr M. Youssef},
title = {A Meet-in-the-Middle Attack on Reduced-Round Kalyna-b/2b},
howpublished = {Cryptology ePrint Archive, Report 2015/762},
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.