@misc{cryptoeprint:2012:603,
author = {Alexis Bonnecaze and Robert Rolland},
title = {Collecting Data while Preserving Individuals' Privacy: A Case Study},
howpublished = {Cryptology ePrint Archive, Report 2012/603},
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.