Date: Mon, 12 Mar 2018 00:14:42 -0400
To: =?UTF-8?Q?JOSE_FEMENIAS_CA=C3=91UELO?= <jose.femenias@gmail.com>,
	Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
From: ZmnSCPxj <ZmnSCPxj@protonmail.com>
Reply-To: ZmnSCPxj <ZmnSCPxj@protonmail.com>
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Subject: Re: [bitcoin-dev] Bulletproof CT as basis for election voting?
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Good morning Jose,

By my understanding, the sender needs to reveal some secrets to the receive=
r, and the receiver will then know if it received 0 or 1 coin from that sen=
der.  (At least from my understanding of MimbleWimble; it might not be the =
case for CT, but MW is an extension of CT so...)

If voters send vote-coins directly to The Party, then The Party knows the v=
otes of particular voters, and may then dispatch subcontractors to dispatch=
 those voters.  It may be possible to have aggregators/mixers, but then you=
 would have to trust the aggregators/mixers operate correctly and send to t=
he correct destination party, and that the mixers are not recording voters.

Maybe in combination with something like CoinSwap or CoinJoin protocol woul=
d work to obscure the source of coins: a voter would have to swap several t=
imes with many, many other voters to ensure increased anonymity set (and th=
en maybe some voters may report their transactions to The Party).

In any case sending directly from the tx of the Voting Authority to another=
 tx to your selected The Party would let The Party members who secretly con=
trol the Voting Authority records to figure out, which voters got which txo=
uts of the Voting Authority (presumably the Voting Authority has strict pub=
lic records of which txout went to which voter, in order to prevent the Vot=
ing Authority secretly giving multiple vote-coins to a single One Man, All =
Votes).

Regards,
ZmnSCPxj


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On March 11, 2018 8:44 PM, JOSE FEMENIAS CA=C3=91UELO via bitcoin-dev <bitc=
oin-dev@lists.linuxfoundation.org> wrote:

> If I understand Bulletproof Confidential Transactions properly, their mai=
n virtue is being able to hide not the senders/receivers of a coin but the =
amount transferred.
>=20
> That sounds to me like a perfect use case for an election.
>=20
> For instance, in my country, every citizen is issued a National ID Card w=
ith a digital certificate.
>=20
> So, a naive implementation could simply be that the Voting Authority, sen=
ds a coin (1 coin =3D 1 vote) to each citizen above 18. This would be an op=
en transaction, so it is easily auditable.
>=20
> 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.
>=20
> In the end, each party will accrue as may votes as coins received.
>=20
> Is there any gotcha I=E2=80=99m missing here? Are there any missing featu=
res required in Bulletproof to support this use case?
>=20
> bitcoin-dev mailing list
>=20
> bitcoin-dev@lists.linuxfoundation.org
>=20
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev