S-money: virtual tokens for a relativistic economy. (arXiv:1806.05884v2 [quant-ph] UPDATED)

We propose definitions and implementations of "S-money" - virtual tokens
designed for high value fast transactions on networks with relativistic or
other trusted signalling constraints, defined by inputs that in general are
made at many network points, some or all of which may be space-like separated.
We argue that one significant way of characterising types of money in
space-time is via the "summoning" tasks they can solve: that is, how flexibly
the money can be propagated to a desired space-time point in response to
relevant information received at various space-time points. We show that
S-money is more flexible than standard quantum or classical money in the sense
that it can solve deterministic summoning tasks that they cannot. It requires
the issuer and user to have networks of agents with classical data storage and
communication, but no long term quantum state storage, and is feasible with
current technology. User privacy can be incorporated by secure bit commitment
and zero knowledge proof protocols. The level of privacy feasible in given
scenarios depends on efficiency and composable security questions that remain
to be systematically addressed.

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