@misc{cryptoeprint:2006:422,
author = {Joern Mueller-Quade and Dominique Unruh},
title = {Long-term Security and Universal Composability},
howpublished = {Cryptology ePrint Archive, Report 2006/422},
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.