Open Vote Network

What is the Open Vote Network?

The Open Vote Network (OV-net) is a 2-round decentralized voting protocol with the following attractive features

• All communication is public - no secret channels between voters are required.
• The system is self-tallying - no tallying authorities are required.
• The voter's privacy protection is maximum - only a full collusion that involves all other voters in the election can uncover the voter's secret vote.
• The system is dispute-free - everybody can check whether all voters act according to the protocol, hence ensuring the the result is publicly verifiable.

A video tutorial on how to deploy and install the Open Vote Network can be found here: https://youtu.be/5wch2_WhPvg

Our paper was published in Financial Cryptography and Data Security 2017: http://fc17.ifca.ai/preproceedings/paper_80.pdf

Our third prize submission to the economist cyber security competition: http://www.economist.com/sites/default/files/newcastle.pdf

A description of the voting protocol can be found here: http://homepages.cs.ncl.ac.uk/feng.hao/files/OpenVote_IET.pdf

This program presents an efficient realization of this protocol over the Ethereum network.

Why Ethereum?

Ethereum is a platform for Smart Contracts that provides the following:

• A public communication channel (i.e. its peer to peer network).
• All communication is authenticated (i.e. transactions are signed by the voter's Ethereum address)
• An immutable public ledger to store the voting information (i.e. eligibility white list, voting keys and votes).
• Economic majority must reach consensus on a program's execution.

The above allows anyone to verify the execution of the program, and that the protocol is executed correctly.

How does it work?

The protocol has five phases.

SETUP

• Election Admin is responsible for sending Ethereum a white list of eligible voters.

SIGNUP

• Voters submit their voting key, and a zero knowledge proof to prove knowledge of the voting key's secret.
• Ethereum verifies the correctness of the zero knowledge proof and stores the voting key.

COMMIT (OPTIONAL)

• Voters submit the hash of their vote.
• Why? In The Open Vote Network - the final voter can compute the tally before everyone else. This might give them an unfair advantage. To prevent this problem, this round can commit the voter to their encrypted vote in advance - so they cannot later change their mind.

VOTE

• Voters submit their ElGamal encrypted vote, and a 1 out of 2 zero knowledge proof that the vote is either 1 or 0. (i.e. yes or no).
• Ethereum verifies the 1 out of 2 zero knowledge proof and stores the vote.

TALLY

• Ethereum computes the tally once all votes have been cast.

How can I pick up this library and go?

Video tutorial: https://youtu.be/5wch2_WhPvg

You need to run 'Geth' in the background:

1. geth <OPTIONAL: --dev/testnet> --rpc --rpcapi="db,eth,net,web3,personal" --rpcport "8545" --rpcaddr "127.0.0.1" --rpccorsdomain "*" console

Example: ./geth --dev --rpc --ipcpath "~/Library/Ethereum/geth.ipc" --rpcapi="db,eth,net,web3,personal" --rpcport "8545" --rpcaddr "127.0.0.1" --rpccorsdomain "*" console

2. Compile the .SOL, and send it to the Ethereum Network.

3. Update vote.html, admin.html livetally.html with the correct abi/contract address.

4. Voters open vote.html, and the Election Admin opens admin.html

5. Each voter requires a voter.txt document that contains the following:

   • x - the private key for the voter's voting key,
   • xG - the voter's voting public key,
   • v - the random nonce for a single ZKP,
   • w,r,d - the random nonces for the 1 out of 2 ZKP.
   • All values should be seperated by commas (i.e. ",") in a .txt document.

6. Voters can register and cast their vote.

An example 'voter.txt' has been included, and a Java Program 'votingcodes.jar' is included that can compute these numbers for the voter.

Some photos of the voting system can be found here:

http://homepages.cs.ncl.ac.uk/patrick.mc-corry/openvotenetwork/

What functions are available?

The voting protocol leverages the following libraries:

ECCMath and Secp256k1: https://github.com/androlo/standard-contracts/blob/master/contracts/src/crypto/Secp256k1.sol DateTimePicker: http://xdsoft.net/jqplugins/datetimepicker/

We have implemented the following:

Schnorr non-interactive ZKP:

• Function should ONLY be called locally. NEVER send transaction to network.
  • createZKP(uint x, uint v, uint[2] xG)
• Send transaction to the network to allow Ethereum to verify
  • verifyZKP(uint[2] xG, uint r, uint[3] vG)

1 out of 2 ZKP:

• Function should ONLY be called locally. NEVER send transaction to network.
  • create1outof2ZKPYesVote(uint w, uint r1, uint d1, uint x)
• Function should ONLY be called locally. NEVER send transaction to network.
  • create1outof2ZKPNoVote(uint w, uint r2, uint d2, uint x)
• Send transaction to the network to allow Ethereum to verify.
  • verify1outof2ZKP(uint[4] params, uint[2] y, uint[2] a1, uint[2] b1, uint[2] a2, uint[2] b2)

Election Functions:

SETUP

• White list a set of addresses. Only Election Admin can call.
  • setEligible(address[] addr)
• Set question and period of time for voters to sign up. Transition from SETUP to SIGNUP Phase. Only Election Admin can call.
  • beginSignUp(string _question, bool enableCommitmentPhase, uint _finishSignupPhase, uint _endSignupPhase, uint _endCommitmentPhase, uint _endVotingPhase, uint _endRefundPhase, uint _depositrequired) inState(State.SETUP) onlyOwner returns (bool){

SIGNUP

• Voters register their voting key. All eligible voters can call.
  • register(uint[2] xG, uint[3] vG, uint r)
• Transition from SETUP to COMPUTE Phase.
  • finishRegistrationPhase()

COMMIT

• Voters send the hash of their vote. All registered voters can call.
• submitCommitment(bytes32 h) inState(State.COMMITMENT) {

VOTE

• Voters submit their vote. All registered voters can call.
  • submitVote(uint[4] params, uint[2] y, uint[2] a1, uint[2] b1, uint[2] a2, uint[2] b2) inState(State.VOTE) returns (bool) {

TALLY

• Compute the final tally. Anyone can call. Transition from VOTE Phase to FINISH Phase.
  • computeTally()

ANY Phase.

• Reset the entire election. Only Election Admin can call.
  • Reset()

What is next?

Ideas:

• Code could be updated to remove the commit stage - if the contract requires the Election Admin to cast the final (dummy and NO) vote!
• Update code to process votes in batches - so we can have more than 50 voters.
• Allow more than just "yes" or "no" as voting options.
• Update unit testing (Should be broken due to recent changes I made).

To Fix:

• We have changed the code since the Economist Challenge... and the unit testing still needs updated.
• GUI was changed during the Economist Challenge (my old and very reliable gui was too geeky/ugly!). It should WORK fine! But bugs might exist... Ideally would like to revamp GUI from scratch. Are you a designer? Get in in touch!

This project demonstrates the current limitation of cryptographic protocols on the Ethereum network.

We need to think of how Ethereum can better natively support cryptography... to avoid the limits we reached.

I release this code under the MIT license https://choosealicense.com/licenses/mit/

p.s. If you find any bugs in our code - then fix it and provide a pull request :) ... or at least tell me about them... patrick.mccorry@ncl.ac.uk