[EM] untraceable receipts

[Ernest Prabhakar]

On Nov 12, 2003, at 4:02 PM, David GLAUDE wrote:
> Forest Simmons wrote:
>>> It is not acceptable for the voter to run out of the voting location
>>> with a receipt. This mean I have something that proof my vote. I 
>>> could
>>> be forced to show my receipt and if I did not vote as I was asked...
>>> face the consequence.
>>>
>>> The secrecy of the vote make it impossible to have a hardcopy you 
>>> take
>>> at home!!! Not even a magic number secretly encoded or else.
>> What if you were given several receipts, and only you know which is 
>> the
>> real one.  One of the fake receipts could be used to satisfy the 
>> mafia.
>
> What was the goal of that receipts???
> 1) To remember who you voted for?
> or
> 2) To verify your vote was counted?
>
> 1) is silly.
> If 2) is possible for you, it is possible for the mafia too. ;-)

I don't get #2 at all.  I've actually been confused by this.  If by 
receipt we mean a full plaintext list of all the votes you made, then I 
can see how it would be a security risk.   However, it would think it 
would be fairly trivial to create an ecrypted receipt that could 
-verify- a vote without actually revealing the vote (at least without 
massive conspiracy).

For example, each vote could be used to create a 'private key - public 
key' pair, as in public key infrastructures (PKI).    The private key 
would be used to hash a cumulative vote tally, and the public key would 
be given to the voter (along with: you are the 1523rd voter).    It 
should be mathematically possible to audit the vote tallies, and for 
the voter to confirm that his private key was used at a given step, 
without revealing any information about the private key.  The first 
voter would hash a random seed, so that even his/her vote would not be 
decipherable.

I may not have all the details right, but given the asymmetry of 
knowledge in PKI there should be some mechanism for separating 
validation from exposure.

-- Ernie P.

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