@misc{cryptoeprint:2000:067,
author = {Ran Canetti},
title = {Universally Composable Security: A New Paradigm for Cryptographic Protocols},
howpublished = {Cryptology ePrint Archive, Report 2000/067},
year = {2000},
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.