@misc{cryptoeprint:2009:384,
author = {Orr Dunkelman and Tor E. Bjørstad},
title = {Practical Attacks on NESHA-256 },
howpublished = {Cryptology ePrint Archive, Report 2009/384},
year = {2009},
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.