This is an example project on how to develop Ethereum smart-contract and client.

Epoll project implements very simple voting system, with quite a few of limitations, as opposed to regular voting system.

In particular, epoll demonstrates following properties:

1. Eligibility: weak. Anybody, who has ethereum account, and can access this system, can vote. So voter might be non-relevant in general. This might be enforced by network organization, or might be addressed n the code itself.

2. Anonymity: pretty strong, unless the same account used for other purports.

3. Confidentiality: weak. Anybody can see other's choices, however there is no link to the person.

4. Vote falsification: strong. It's computationally unfeasible to cast a vote under other person's account, due to use state-of-art Public key cryptography.

5. Tamper proof: strong. It's computationally unfeasible to change data in the storage due to blockchain properties.

This scenario runs both ethereum node and client application in localhost-only truffle debug environment.

ATTENTION: In order to run the demo node.js and npm should be installed.

Truffle is a framework to write, debug, and test both ethereum smart-contracts and applications, written in JavaScript.

### Check out git repository:
$ git clone [email protected]:osesov/epoll.git
$ cd epoll

### Install necessary components
$ npm install

### Run ganache: local ethereum client, used to test ethereum applications. 
$ ./node_modules/.bin/ganache-cli
Ganache CLI v6.3.0 (ganache-core: 2.4.0)

Available Accounts
....
Listening on 127.0.0.1:8545

### In another console, deploy smart contracts truffle
$ cd epoll
$ ./node_modules/.bin/truffle migrate

### and finally run e-vote test:
$ ./node_modules/.bin/truffle test

  Contract: epoll
CA: Create poll on 'How would like your eggs?'. Choices:
CA:     0) 'Sunny Side Up'
CA:     1) 'Over Easy'
CA:     2) 'Poached'
CA:     3) 'I don't care!'
CA: Poll address: 0xA810Ad443011483098c3cfd2701F8dF1B7FB4816
V1: voting from 0xdD1805BC74fAD79595E9094b4350b42b0073a427 for 2. outcome 0(accepted)
V2: voting from 0x137217e4fBa37ff77C384C50be8Eff1abAeee3a0 for 3. outcome 0(accepted)
V3: voting from 0xaE55d15B0054F513B8006668B33543714e0A2AAD for 2. outcome 0(accepted)
V4: voting from 0x671E1876A538f0261d58FF503B7236B49761173b for 2. outcome 0(accepted)
V5: voting from 0x6a7833CbcD3360cF9f79f4d5FEa6E778785d211B for 3. outcome 0(accepted)
V6: voting from 0xB3e3494f9287642026a024a3EE428aa16055E51b for 1. outcome 0(accepted)
V7: voting from 0xa612E6E61a298A5C90fBbE68D7A1Afa5b466DDfB for 0. outcome 0(accepted)
V8: voting from 0x16c5E4E127803b1Ed1e2633F9892Dfe3648940fa for 0. outcome 0(accepted)
V9: voting from 0x5c10685703357e3628F763f257A3FF7b47Ed0583 for 0. outcome 0(accepted)
CA: === Poll choice (3 votes) ===
CA:     0) 'Sunny Side Up'
CA:     2) 'Poached'
CA: --- Others ---
CA:     3) 'I don't care!': 2
CA:     1) 'Over Easy': 1
    ✓ vote (520ms)


  1 passing (531ms)

для проведения демонстрации нужно:

1. Поставить node.js (https://nodejs.org/)

2. в корневой папке проекта запустить npm install. Эта команда поставить все необходимые компоненты

3. запустить скрипт mkweb из корня. Этот скрипт подготавливает в папке web два интерфейса: организатора (web/ca) и голосующего (web/voter).

4. запустить сервис блокчейна, который используется для проведения демонстрации: node_modules/.bin/ganache-cli

5. запустить все вебприложения, открыв их в браузере web/ca/ca.html и web/voter/voter.html

6. после этого можно создавать в приложении ca голосования, voter будет получать оповещения и создании и закрытии голосования автоматически. После создания голосования voter даст возможность проголосовать и по закрытии голосования отобразит результат голосования. Возможность зачитать существующие голосования из блокчейна в данный момент не реализована.

Source code:

• contracts/epoll.sol: ethereum smart-contract code, written in solidity.

• test/poll.js: poll client module, written in JavaScript. This module consists of two classes: CA and VOTER.

  class CA implements Central Authority handling - the service, which creates a poll and is responsible for maintaining it.

  Methods provided:

  • startPoll: create a new poll.
  • endPoll: complete a poll, so it could not be voted any more
  • getResults: Read results from the poll.

  class VOTER implements voter functionality.

  • vote: cast a vote. Vote is accepted if this voter has made no choice yet and the casted vote is in a valid range. All these limitations are enforces at blockchain side, in the smart contract. Finally vote emits event to the sender with the voting outcome (if it was accepted or not).
  • getResults: Read results from the poll.

• test/utils.js: some Ethereum utils, used in poll client implementation.

• test/epoll.js: truffle JavaScript test for the epoll smart-contract.