@misc{cryptoeprint:2009:584,
author = {Yu Liu, Kaijie Wu, and Ramesh Karri},
title = {Scan-based Attacks on Linear Feedback Shift Register Based Stream Ciphers},
howpublished = {Cryptology ePrint Archive, Report 2009/584},
year = {2009},
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.