@misc{cryptoeprint:2005:175,
author = {Yassir Nawaz and Kishan Chand Gupta and Guang Gong},
title = {A 32-bit RC4-like Keystream Generator},
howpublished = {Cryptology ePrint Archive, Report 2005/175},
year = {2005},
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.