Block Contract

Block contract is to build decentralized contract that people can sign, view and trust. To protect the privacy, the content of the contract will NOT be hosted in the blockchain, only the hash of the content is store in the chain.

High level design

The prototype of the flow of the app looks like this:

Contract Templates

Accord Project is a great open source tool to generate legal contracts. The ultimate goal is integrate this project with Accord Legal Contract Template Studio.

Blockchain

We will use ArcBlock's Blockchain Framework to build a custom blockchain for this project's demo. The block explorer lives here: Block Contract Block Explorer

It's possible to use other blockchains, such as Ethereum, Bitcoin to record the contract through Open Chain Access Protocol (OCAP), but it will be limited in features.

DB schema for contract

For contract created by the user, we store it as the following schema in mongo:

const ContractSchema = new mongoose.Schema({
  // the did is calculated by sha3(concat(content, hash, signatures list without each sig))
  _id: { type: String, required: true, trim: true },
  requester: {type: String, required: true, trim: true},
  synopsis: { type: String, required: true, trim: true },
  content: { type: Buffer, required: true },
  hash: { type: String, required: true },
  signatures: [{
    name: { type: String, required: true, trim: true },
    email: { type: String, required: true, trim: true },
    signedAt: { type: Date },
    signature: { type: Buffer }
  }],
  finished: { type: Boolean, default: false},
  address: { type: String, default: '' },
  createdAt: { type: Date },
  updatedAt: { type: Date },
});

Run this project from Repo

Requirements

• Node.js v10+

Get code and install dependencies

cd block-contract
make dep
node tools/declare.js

Prepare the configuration

Before running the app, you need to put a .env file into your repo:

cat > .env
SKIP_PREFLIGHT_CHECK=true

DATA_DIR=".data"
APP_TOKEN_SECRET="c196792a8a14be2d3f10646079001a37e634ebbd99643c543f"
APP_TOKEN_TTL="1d"
APP_PORT="3030"
APP_SK="0x4848947cc88b2e83682dec00e681d9ca057c582c0bc9fd42a1ce6c386361d2bda24f683f458bad332b2c913fd374493b08aca1993f2640cbfccd962951c220c0"
APP_ID="zNKaoF3y3MiDHkisK2Dt8FgGVY6dXP6XETQr"

CHAIN_ID="playground"
CHAIN_HOST="https://playground.network.arcblockio.cn/api"

REACT_APP_APP_NAME="Block Contract"
REACT_APP_APP_DESCRIPTION="A decentralized contract platform that people can sign, view and trust"
REACT_APP_BASE_URL="http://192.168.1.2:3030"
REACT_APP_API_PREFIX=""

MAILGUN_USER="<your mailgun user>"
MAILGUN_PASSWORD="<your mailgun password>"

Note that you need to put your gmail user/pass and tune the BASE_URL here.

Make sure that you have your cellphone installed ABT Wallet and it is under the same WIFI as your laptop running the app. Then:

Start the Block Contract app

make run

Screen Shots

Pages are being added so screen shots will be gradually available:

The home page

Step 1: Scan QR code to login (provided by Forge React Starter kit)

After you scanned the QR code with ABT wallet:

Then you are redirect to profile page. User can see the existing contracts:

Step 2: Create a new contract

You may want to create a new contract:

And all the signers will go emails like this:

Step 3 (for signer): Sign the contract

As a signer, when you got the email, if you click the "View the Contract" button or the link, you will get:

Then scan the QR code with the wallet app:

Once accepted, you signature will be put into the agreement. If all parties finished signing, the doc is signed:

Step 4 (anyone): Verify the contract in the chain

Then anyone can check the signatures on the chain:

We could make this view much better later on.