@misc{cryptoeprint:2005:082,
author = {Lars R. Knudsen},
title = {Some properties of an FSE 2005 Hash Proposal},
howpublished = {Cryptology ePrint Archive, Report 2005/082},
year = {2005},
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.