@misc{cryptoeprint:2011:577,
author = {Ou Ruan , Cai Fu and Guohua Cui },
title = {An Efficient Protocol for the Commit-Prove-Fair-Open functionality },
howpublished = {Cryptology ePrint Archive, Report 2011/577},
year = {2011},
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.