@misc{cryptoeprint:2012:103,
author = {Marten van Dijk and Ari Juels and Alina Oprea and Ronald L. Rivest},
title = {FlipIt: The Game of "Stealthy Takeover"},
howpublished = {Cryptology ePrint Archive, Report 2012/103},
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.