@misc{cryptoeprint:2010:387,
author = {Goutam Paul and Subhamoy Maitra and Shashwat Raizada},
title = {A Combinatorial Analysis of HC-128},
howpublished = {Cryptology ePrint Archive, Report 2010/387},
year = {2010},
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.