@misc{cryptoeprint:2004:078,
author = {Tadayoshi Kohno},
title = {Analysis of the WinZip encryption method},
howpublished = {Cryptology ePrint Archive, Report 2004/078},
year = {2004},
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.