@misc{cryptoeprint:2006:460,
author = {Donghoon Chang},
title = {Preimage Attacks On Provably Secure FFT Hashing proposed at Second Hash Workshop in 2006},
howpublished = {Cryptology ePrint Archive, Report 2006/460},
year = {2006},
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.