Credible Chain

This is a blockchain to store an tally all the votes from the credible choice project. The main point is to provide an immutible audit trail of all events, to provide more confidence in the veracity of the election results.

Overview

We run the blockchain using Tendermint in PoA mode. That is we will hardcode likely 4 validators at the genesis of the chain, which will run the validating nodes. These nodes should be run by independent entities to prevent collusion, but more importantly, they provide a signed record that can be synced and verified by anyone running a full-node. We will provide details on how to connect an "audit" node.

The state machine has one operation - set vote, which will add or update the vote for that particular person. We use a unique id derived from the mobile phone number provided from the gateway to prevent double-voting. If we get a second request with the same id, we change the previous vote, rather than adding a new one.

We allow a fixed set of keys (stored on the api server) to sign a vote transaction as a witness. We will also include the sms code, as well as a unique transaction id from the sms gateway in order to allow people to spot-check transactions and verify that everything is being done legitimately. This is the main purpose of the blockchain - to provide a fully transparent, public ledger.

Building the command

You can install all dependencies, run tests, and compile a new image simply by checking out this repo and running:

make all

You can build a docker image with the current commit (ideally on a tag) with:

make dist

Check the docker image is build properly...

docker images | grep credchain
docker run confio/credchain version

docker images | grep tallybox
docker run confio/tallybox version

Set up the system

We need to set this up with some keys in order to initialize the blockchain properly. We will assume you have the binaries installed, but it works the same with docker... Just use docker run confio/tallybox instead of tallybox

KEY=$(tallybox keys)
tendermint init --home=$HOME/.credchain
credchain init $KEY

Running the chain

tendermint node --home=$HOME/.credchain --proxy_app=tcp://localhost:11111 > tendermint.log &
credchain start -bind=tcp://localhost:11111 > credchain.log & 

Running the server

tallybox start -port=5005 -remote=http://localhost:26657

Trying it out

HOST=localhost
# HOST=134.209.88.159
curl http://$HOST:5005
curl http://$HOST:5005/tally
curl -X POST http://$HOST:5005/vote --data '{}'
curl -X POST http://$HOST:5005/vote --data '{"vote":{"main_vote":1,"rep_vote":"BR1","charity":"MD","postCode":"SW16","birth_year":1980,"donation":100},"identifier":"xxx123456xxx","sms_code":"BA383SKD 10","voted_at":"2019-02-21T13:27:20.070566467Z"}'
curl http://$HOST:5005/tally

Deployment Example

scp -r ops user@host:ops
ssh user@host
./ops/install.sh
source .bash_aliases
./ops/init.sh
# note that run will install systemd services, so it will auto-restart on reboot
./ops/run.sh

Blockchain Design

We build the application using the weave framework, using their signature and multisig modules, and adding a custom vote extension for our needs. The data we store is:

type VoteRecord struct {
    Vote Vote // the important info, see above...
    Identifier string // unique anonymized id from sms gateway
    SMSCode string // the human words eg. "hungry horse fly" that were texted (for auditing)
    TransactionID string // a unique id from the sms gateway to look up this exact message was sent
    VotedAt time.Time // when the vote was cast  
}

Note that the Vote structure is defined in the main application docs

We define a set of notaries in the genesis file, and any submitted VoteRecord must be signed by at least one of them. If the Identifier was not present, add this record and add the votes to the tally. If the Identifer was already present, subtract the votes in previous record and add the new votes to the tally, then update the record. All history data is stored in the transactions as well, we just need to maintain the last vote and tally in the blockchain db.

APIs

We must provide a client API in golang to encode, sign, and submit transactions. This will be exported by this repository with the goal of being imported by the API server, to be used with a private key stored there.

If desired, we can extend iov-core to provide a TypeScript REPL allowing exploration and ad-hoc queries of the current blockchain state (as well as transaction history). Or any other solution to audit that is desired.