Message-ID: <1520847175.2339.14.camel@mmci.uni-saarland.de>
From: Tim Ruffing <tim.ruffing@mmci.uni-saarland.de>
To: bitcoin-dev@lists.linuxfoundation.org
Date: Mon, 12 Mar 2018 10:32:55 +0100
In-Reply-To: <90096274-9576-4A08-A86A-E1C4F3E3B5DE@gmail.com>
References: <90096274-9576-4A08-A86A-E1C4F3E3B5DE@gmail.com>
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Subject: Re: [bitcoin-dev] Bulletproof CT as basis for election voting?
Precedence: list

You're right that this is a simple electronic voting scheme. The thing
is that cryptographers are working on e-voting for decades and the idea
to use homomorphic commitments (or encryption) and zero-knowledge
proofs is not new in this area. It's rather the case that e-voting
inspired a lot of work on homomorphic crypto and related zero-knowledge 
proofs. For example, range proofs are overkill in e-voting. You just
need to ensure that the sum of all my votes (over all candidates) is 1.
 
E-voting protocols typically require some "bulletin board", where
ballots are stored. A blockchain could indeed be helpful in specific
cases (but not in all cases)...

If you're interested in that stuff, I'd suggest you to read some
literature about e-voting. (For example, 
https://arxiv.org/pdf/1801.08064 looks interesting for the connection
to blockchains -- I haven't read it though). There are pretty
sophisticated protocols in the literature. And I think that this
mailing list may not be the best place to discuss these.

Best,
Tim 


On Sun, 2018-03-11 at 13:44 +0100, JOSE FEMENIAS CAÑUELO via bitcoin-
dev wrote:
> If I understand Bulletproof Confidential Transactions properly, their
> main virtue is being able to hide not the senders/receivers of a coin
> but the amount transferred.
> That sounds to me like a perfect use case for an election.
> For instance, in my country, every citizen is issued a National ID
> Card with a digital certificate. 
> So, a naive implementation could simply be that the Voting Authority,
> sends a coin (1 coin = 1 vote) to each citizen above 18. This would
> be an open transaction, so it is easily auditable.
> Later on, each voter sends her coin to her preferred party, as part
> of a Bulletproof CT, along with 0 coins to other parties to disguise
> her vote.
> In the end, each party will accrue as may votes as coins received.
> 
> Is there any gotcha I’m missing here? Are there any missing features
> required in Bulletproof to support this use case?
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