Re: Proposal 165: Easy migration for voting authority sets

[Paul Syverson <syverson@xxxxxxxxxxxxxxxx>]

Hi Nick et al.,

Two things:

1. I think you mean that an authority votes with whatever the largest
set is that it lists that is listed by the most members of that set. 
(I added "largest" to your criterion.)

I guess there is an ambiguity of 'most' but if you have a set and a
proper subset, both of which are listed by all the members of each,
then the ones in the smaller set have no basis to prefer the larger
one and will never drop the smaller one. If by 'most' you implicitly
mean biggest rather than largest fraction, it is confusing since
it is no longer relative to the givne voting set but relative to
others.


2. More significantly, there is something I don't get about the
proposal. I think I understand the problem with proposal 134. It seems
like a standard byzantine failure when there are not at least 3n+1
honest and correct voters, where n is the number of dishonest, but I
didn't look at it closely to see if there are some differences.

The new proposal is not that bad, but it still allows a single
hostile authority to prevent the addition of a new authority.

If Alice does not want to add authority Bob, then she
refuses to make a voting set containing him. Other honest-correct
authorities will not prefer the new voting set until some of them drop
the old one that did not have Bob in it. But none of them should
ever do that because the voting set without Bob in it is preferred by
a larger majority of its members.

If 'most' is interpreted as discussed in 1. above, the same problem
applies, but you need two hostile authorities to make sure Bob can never
get in no matter what the rest of the authorities do.

Similarly, if the honest authorities want to drop Bob, as long as two
existing authorities (possibly but not necessarily one being Bob) want
to maintain him, then none should ever delist the larger set because
it will always be preferred over the smaller one. So he won't
get dropped.

What am I missing?

aloha,
Paul