  Nakamoto consensus, the protocol underlying Bitcoin, has the potential to
secure a new class of systems which agree on non-mathematical truths. As an
example of this capability, we propose a design for a trustless, data
availability oracle. This exposition reduces the problem of determining whether
or not a registered datum is publicly available to the problem of constructing
a network in which either almost all nodes can download a given datum, or
almost none of them can.
