@misc{cryptoeprint:2006:189,
author = {D. R. Stinson},
title = {Unconditionally secure chaffing and winnowing with short authentication tags},
howpublished = {Cryptology ePrint Archive, Report 2006/189},
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.