william(at)elan.net [william(_at_)elan(_dot_)net] wrote:
Its pretty standard practice that re-voting should not be allowed.
But only because most elections are anonymous, so a re-voter's prior votes
cannot be discarded.
So while if its an accident its not a big deal and we should ignore
multiple copies its also possible for somebody to change his mind after
talking to others (especailly bad if it happens in-mass) and possibility
of this and other manipulation schemes should be minimized.
How can you consider talking to others and changing your mind a
"manipulation scheme"?? This is normal democratic practice and has
nothing to do with manipulating elections.
And as you correctly noted somebody may try technical means to
change/invalidate somebody elses vote by sending bad extra confirmations
and hope that one of them is right and gets to be accepted by the
system.
This argument doesn't hold.
If you allow only one vote and invalidate _all_ of my votes as soon as I
cast another vote, an attacker can try to invalidate my vote by casting a
forged vote before or after I submit my real vote. The attacker's chances
of submitting before or after me are 100%.
If you allow multiple votes and only count the first, an attacker can try
to forge my vote by simply submitting the forged vote before I manage to
submit my real vote. The attacker's chances of submitting first are about
50%.
If you allow multiple votes and only count the last, an attacker can try
to forge my vote by simply submitting a forged vote after every real vote
I submit. The attacker's chances of submitting last are about 50%.
It makes no difference whatsoever. The point is that we plan to prevent
forged votes in the first place, and assuming we succeed in doing that,
all alternatives are equivalent, except that with the third option voters
have the change to change their mind before the election is over. I
consider that a good thing.