@misc{cryptoeprint:2015:959,
author = {Jian Zou, Le Dong},
title = {Cryptanalysis of the Round-Reduced Kupyna Hash Function},
howpublished = {Cryptology ePrint Archive, Report 2015/959},
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.