@misc{cryptoeprint:2012:449,
author = {Johannes Braun and Johannes Buchmann and Ciaran Mullan and Alex Wiesmaier},
title = {Long Term Confidentiality: a Survey},
howpublished = {Cryptology ePrint Archive, Report 2012/449},
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.