@misc{cryptoeprint:2012:380,
author = {Ioana Boureanu and Serge Vaudenay},
title = {Several Weak Bit-Commitments Using Seal-Once Tamper-Evident Devices},
howpublished = {Cryptology ePrint Archive, Report 2012/380},
year = {2012},
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.