@misc{cryptoeprint:2006:437,
author = {An Braeken, Ventzislav Nikov, Svetla Nikova},
title = {On Zigzag Functions and Related Objects in New Metric},
howpublished = {Cryptology ePrint Archive, Report 2006/437},
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.