@misc{cryptoeprint:2014:985,
author = {Bartosz Zoltak},
title = {Statistical weakness in Spritz against VMPC-R: in search for the RC4 replacement},
howpublished = {Cryptology ePrint Archive, Report 2014/985},
year = {2014},
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.