In contrast to existing techniques, this approach involves an interactive
protocol between protestors and witnesses. This change in approach makes a
practical evaluation very important.
The performance section relies on pieces of individually evaluated
primitives that were presented in other works. While the current discussion
does give a sense for the performance one would expect, it would be far
more convincing that this approach is feasible if the authors would take a
step further and implement the key modules in their protocol. (for example,
would even local communication with tens of thausands of condensed cell
phones be feasible?)
Using trusted witnesses, on the other hand, has similar pitfalls to the
existing approaches, as discussed in the prior work section: it is hard
to find witnesses that all opposing factions will trust, and it is hard
to scale this approach to large crowds. Since the distance-bounding
protocol is not specified in this paper, it is hard to assess its
practical limitations, but typical phone-to-phone communications have
relatively small range, so to count all participants in a large protest
witnesses need to be deployed throughout the protest.