QuorumSample_DApp

Pre-requisites:
- Docker version 18.09.0+
- docker-compose version 1.23.2+
- Node.js v8.5+
- Truffle v4+
- IDE of Your choice (preferred is VsCode)

Index

Introduction
Network Architecture
The Flow and Idea
Smart Contract
How Quorum Is Maintaining the Privacy
Steps t start the Quorum Blockchain
Steps to Deploy the Smart Contracts for he Bidder Dapp
Steps to start the server
Swagger for interaction with the server
Conclusion and what next?

1. Introduction:-

Its a simple dapp demo over Quorum Blockchain, which utilizes a dockerized environment to host the Quorum Blockchain and have its smart contracts written in Solidity 0.4.17 and handles deployments with truffle smart contract deployment/development framework and it has a NodeJS server to serve the APIs for feature interactions with the smart contract and it has a Swagger UI to provide UI interface / Documentation.

2. Network Architecture:-

There is a dockerized environment forked from quorum's official repo for maintaining the dockerized environment for the quorum dapp network.

Basically there are 7 Nodes, and their respective tx managers, for further details you can study the docker-compose file attached in this sample project.

3. The Flow and Idea

The Bidder DApp: Our Sample Dapp basically utilizes,

Three quorum nodes
- NodeA
- NodeB
- NodeC

NodeA will be the owner of the item to be placed bids for and to allow the users to do that it first had to create that item with a non-zero base price. Now, NodeB and NodeC user/account can place a bid against the base price of the item. Because we have two separate smart contarcts deployed with the truffle migration file

var NodeB = artifacts.require("./NodeB.sol");
var NodeC = artifacts.require("./NodeC.sol");

module.exports = function(deployer) {
  deployer.deploy(NodeB, {
    privateFor: ["QfeDAys9MPDs2XHExtc84jKGHxZg/aj52DTh0vtA3Xc="]
  });

  deployer.deploy(NodeC, {
    privateFor: ["1iTZde/ndBHvzhcl7V68x44Vx7pl8nwx9LqnM/AfJUg="]
  });
};

Here you can see that NodeB smart contract is deployed with an additional parameter of privateFor with the public key of the NodeB QfeDAys9MPDs2XHExtc84jKGHxZg/aj52DTh0vtA3Xc= as its value which means all transactions on this smart contract will be private among the nodeA (as we are deploying smart contarcts from the user/account of nodeA) and nodeB, the other users/accounts of other nodes will not be able to see the transactions made by other nodeB's users.

similarly we have deployed smart contract NodeC with the public key of the nodeC.

4. Smart Contract

For NodeB

pragma solidity ^0.4.17;

contract NodeB {

    struct Bids {
        string itemName;
        uint bid;
        address bidder;
    }
    address private owner;
    
    constructor() public {
        owner = msg.sender;
    }
    
    modifier onlyOwner(address _owner) {
        require(_owner == owner, "cannot perform action.");
        _;
    }

    mapping (string => uint) Items;
    mapping (string => mapping (address => Bids)) itemAddressBids;

    modifier addressNotBlank(address add){
        require(add != 0x0, "null address");
        _;
    }

    modifier nullStringCheck(string memory val){
        require(bytes(val).length > 0, "empty string");
        _;
    }

    modifier uintNonZero (uint val) {
        require(val > 0, "cannot be zero");
        _;
    }
    
    function createItem(string memory name, uint price) public 
    onlyOwner(msg.sender)
    nullStringCheck(name)
    uintNonZero(price) 
    {
        Items[name] = price;
    }
    
    function placeABid(string memory name, uint bid, address bidderAddress) public 
    nullStringCheck(name) 
    uintNonZero(bid)
    {
        require(bid > Items[name], "the bid should exceed the price.");
        
        Bids memory bids = Bids(name, bid, bidderAddress);
        itemAddressBids[name][bidderAddress] = bids;
    }
    
    function getItemPrice(string memory name) public view returns (uint itemPrice){
        return Items[name];
    }
    
    function getBidsForItem(string memory name, address bidderAddress) 
    public 
    addressNotBlank(bidderAddress)
    view 
    returns (string memory itemName, uint latestUserBid)
    {
        return (itemAddressBids[name][bidderAddress].itemName, itemAddressBids[name][bidderAddress].bid);
    }
}

For NodeC

pragma solidity ^0.4.17;

contract NodeB {

    struct Bids {
        string itemName;
        uint bid;
        address bidder;
    }
    address private owner;
    
    constructor() public {
        owner = msg.sender;
    }
    
    modifier onlyOwner(address _owner) {
        require(_owner == owner, "cannot perform action.");
        _;
    }

    mapping (string => uint) Items;
    mapping (string => mapping (address => Bids)) itemAddressBids;

    modifier addressNotBlank(address add){
        require(add != 0x0, "null address");
        _;
    }

    modifier nullStringCheck(string memory val){
        require(bytes(val).length > 0, "empty string");
        _;
    }

    modifier uintNonZero (uint val) {
        require(val > 0, "cannot be zero");
        _;
    }
    
    function createItem(string memory name, uint price) public 
    onlyOwner(msg.sender)
    nullStringCheck(name)
    uintNonZero(price) 
    {
        Items[name] = price;
    }
    
    function placeABid(string memory name, uint bid, address bidderAddress) public 
    nullStringCheck(name) 
    uintNonZero(bid)
    {
        require(bid > Items[name], "the bid should exceed the price.");
        
        Bids memory bids = Bids(name, bid, bidderAddress);
        itemAddressBids[name][bidderAddress] = bids;
    }
    
    function getItemPrice(string memory name) public view returns (uint itemPrice){
        return Items[name];
    }
    
    function getBidsForItem(string memory name, address bidderAddress) 
    public 
    addressNotBlank(bidderAddress)
    view 
    returns (string memory itemName, uint latestUserBid)
    {
        return (itemAddressBids[name][bidderAddress].itemName, itemAddressBids[name][bidderAddress].bid);
    }
}

5. How Quorum Is Maintaining the Privacy

Image below is from the official quorum repo:-

6. Steps to start the Quorum Blockchain

First clone this repo into your machine

git clone https://github.com/NRajTheGeek/QuorumSampleApp.git

and

cd quorum-examples

now to start the dockerized environment and the quorum blockchain 7 node and 7 tx mnager network up and running:

docker-compose up -d

now wait for 5 or 10 min for all nodes to start mining properly, now that we have the network up and running we can now depoy our smart contracts on it.

before moving on further, go through this link and study how to deploy solidity smart contracts on quorum blockchain nodes.

https://truffleframework.com/tutorials/building-dapps-for-quorum-private-enterprise-blockchains

7. Steps to Deploy the Smart Contracts for the Bidder Dapp

Bofore moving forward install truffle globaly with npm.

npm install truffle -g

Now, there are two smart contracts in the contracts directory:

contracts
   Migrations.sol
   NodeB.sol
   NodeC.sol

which are displayed above at the 4th index [smart contracts].

lets have a look on our truffle.json file


module.exports = {
  networks: {
    nodeA: {
      host: '127.0.0.1',
      port: 22000, 
      network_id: '*',
      gasPrice: 0,
      gas: 4500000
    },
    nodeB: {
      host: '127.0.0.1',
      port: 22001, 
      network_id: '*',
      gasPrice: 0,
      gas: 4500000
    },
    nodeC: {
      host: '127.0.0.1',
      port: 22002, 
      network_id: '*',
      gasPrice: 0,
      gas: 4500000
    },
    node4: {
      host: '127.0.0.1',
      port: 22003, 
      network_id: '*',
      gasPrice: 0,
      gas: 4500000
    }
  }
}

Now to deploy these using truffle framework first do a compile from the project root directory

truffle compile

And now you can deploy the smart contracts from project root directory

truffle compile --network nodeA

you should see output similar to

Using network 'nodeA'.

Running migration: 1_initial_migration.js
  Deploying Migrations...
  ... 0xb62991b10c7c39af1603164a35b7e34dd530e9c933781c8fd9da8465b1f0229e
  Migrations: 0x1932c48b2bf8102ba33b4a6b545c32236e342f34
Saving successful migration to network...
  ... 0x7f6c7e9834a9f52ec1bd026a22303ace02506c767199db7e262089523b4737c7
Saving artifacts...
Running migration: 2_deploy_contracts.js
  Deploying NodeB...
  ... 0xd47f328fc16eb28fc9e94e36166234252629a702d82ff5369a019ee690d5f8cc
  NodeB: 0x9d13c6d3afe1721beef56b55d303b09e021e27ab
  Deploying NodeC...
  ... 0x5bf35a010b9b779b38210af7347586cabff9faef8bc337fa22e16acc3e2a72a1
  NodeC: 0xd9d64b7dc034fafdba5dc2902875a67b5d586420
Saving successful migration to network...
  ... 0x7fe29077aa04a72a4b85b10c877d5b43fe1bba655fba5d0bace8ac42b67e6e4b
Saving artifacts...

with obviously contract addresses and tx hashes changed. Now you can launch the Node JS server.

8. Steps to start the server

From Project root directory

npm start

Now the server has started, aps can be accessed at localhost on port 3000.

9. Swagger for interaction with the server

To interact with the APIs there is a Swagger UI hosted which dobles as a clean documentation for this server's APIs.

Go to the following link at your browser.

localhost:3000/swagger

Now first NodeA user must craete an Item with a price for both the nodes: nodeB and nodeC So the accounts on nodeB and NodeC can view this item and the base price and thus a bid can be placed agains the base price. Now, from swagger UI

nodeA will create an item with a non-zero using the createItem post API for both nodeB and nodeC.
nodeB/nodeC can view this item and its base price from swagger UI with the API of getIemPrice to place a bid using the name of the item as identifier (item name).
Now nodeB/nodeC user can place an itegeral bid price higher than the base price of the item from the swagger UI using the placeBid API

Note: The use case of the Quorum protocol allow us to hide the bid of nodeB user from nodeC user, using the txManagers.

10. Conclusion

Now the bid placed by the user/account nodeB can not see the bid placed by the user/account of nodeC which maintains the privacy of info among these node's users/acounts with the nodeA users.

What's next?

This is just to demo the concept of the private transactions over the quorum blockchain network and it is promising in this regard. We obviously need to improve this alot if we want to make an awesome demo app but even in the current stag it proves the concept.

If You have Ideas of improvement please email me at:

[email protected]

charry1729 / quorumsampleapp Goto Github PK

quorumsampleapp's Introduction