Trusted witness version, untrusted witness version

[dbosk]

[dbosk]

A key concern I have is the reliance on witnesses to authenticate
participation. The authors suggest that either trusted witnesses are used
or some number of untrusted ones. I do not see how untrusted witnesses
can lead to a secure outcome, even if there is a large number of them,
since there is no reason not to believe that all of them are colluding
to inflate the crowd size.

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.