@misc{cryptoeprint:2013:266,
author = {Jing Lv and Dongdai Lin},
title = {L-P States of RC4 Stream Cipher },
howpublished = {Cryptology ePrint Archive, Report 2013/266},
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.