@misc{cryptoeprint:2014:174,
author = {T.D.B Weerasinghe},
title = {Analysis of a Modified RC4 Algorithm},
howpublished = {Cryptology ePrint Archive, Report 2014/174},
year = {2014},
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.