  Decoy Routing, the use of routers (rather than end hosts) as proxies, is a
new direction in anti-censorship research. Decoy Routers (DRs), placed in
Autonomous Systems, proxy traffic from users; so the adversary, e.g., a
censorious government, attempts to avoid them. It is quite difficult to place
DRs so the adversary cannot route around them for example, we need the
cooperation of 850 ASes to contain China alone. In this paper, we consider a
different approach. We begin by noting that DRs need not intercept all the
network paths from a country, just those leading to Overt Destinations, i.e.,
unfiltered websites hosted outside the country (usually popular ones, so that
client traffic to the OD does not make the censor suspicious. Our first
question is; How many ASes are required for installing DRs to intercept a large
fraction of paths from, e.g., China to the top n websites (as per Alexa)? How
does this number grow with n? Few ASes (approx. 30) intercept over 90% of paths
to the top n sites, for n = 10, 20...200. Our first contribution is to
demonstrate with real paths that the number of ASes required for a world-wide
DR framework is small (approx. 30). Further, censor nations attempts to filter
traffic along the paths transiting these 30 ASes will not only block their own
citizens, but others residing in foreign ASes. Our second contribution in this
paper is to consider the details of DR placement: not just in which ASes DRs
should be placed to intercept traffic, but exactly where in each AS. We find
that even with our small number of ASes, we still need a total of about 11,700
DRs.We conclude that, even though a DR system involves far fewer ASes than
previously thought, it is still a major undertaking. For example, the current
routers cost over 10.3 billion USD, so if DR at line speed requires all new
hardware, the cost alone would make such a project unfeasible for most actors.
