@misc{cryptoeprint:2013:768,
author = {Bartosz Zoltak},
title = {VMPC-R Cryptographically Secure Pseudo-Random Number Generator Alternative to RC4},
howpublished = {Cryptology ePrint Archive, Report 2013/768},
year = {2013},
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.