Re: The trouble with triples. (Was Three ballot

From: Charlie Strauss <cems_at_earthlink_dot_net>
Date: Wed Sep 27 2006 - 08:31:40 CDT

Kathy and Kurt,

Here's a little more details on how Rivest's scheme works to answer
your questions

first Kurt, The terminolgy "against" is off-putting, I agree.
Though I see why he chose it:it's hard to invent a better term for
what Rivest means. He means literally you are "voting not for",
because on his ballot you have to make marks for people you do not
wish to win. He had to have a term for that positive action, so I
guess he called it voting "against".

This may be come more clear as I answer kathy's question.

So let's review: in every race you have to mark one oval for people
you don't want to win (AKA vote against) and two ovals for the
candidate you do want to win. The ballot is then trisected.

Looking at any given ballot the scanner can't tell if an oval was
part of a vote "for" or a "vote" against. Instead for any oval it
sees, it simply increments the counter for that candidate.

Now what happens is that every time 3 ballots are inserted, then on a
properly marked ballot, at least one oval for every candidate is
filled. Thus no matter what the counter for each candidate
increments one tick for every voter. and the voter's preferred
candidate increments two ticks.

thus at the end of the day candidate each candidates total is
N+(number of votes for)
where N is the number of voters.

If you want you can subtract N from each candidate's totals, then you
are left with simply the number of votes for.

SO now you can see why he has this elaborate "vote checker" that
verifies the 3ballot is of valid form (all the candidates must have
an oval checked, only one candidate has two ovals checked, and none
has three ovals checked). And only after that validation can the
voter insert the 3 strips into the vote counting machine.

Of course since rivest wants physical separation of the checker and
counter (because of his desiderata that the counter can be blind to
which ballot strips go together) And there's a problem. The voter
might modify the ovals after it was checked, or switch one of the
ballot strips for another in his pocket, and thus be able to fill in
more ovals for his favorties and remove ovals for those he opposes,
and thus vote multiple times.

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Received on Sat Sep 30 23:17:07 2006

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