With Chainstack, create a public chain project.

With Chainstack, join the Ethereum Sepolia testnet.

With Chainstack, access your Ethereum node credentials.

With Truffle, create and compile the DApp contract.

With Truffle, deploy the contract to your local development network.

With Truffle, interact with the contract on your local development network.

With Truffle, create and run the contract test.

With Truffle, deploy the contract to your Ethereum node running with Chainstack.

On your machine, create a directory for the contract. Initialize Truffle in the directory:

truffle init

This will generate the Truffle boilerplate structure:

.
├── contracts
│   └── .gitkeep
├── migrations
│   └── .gitkeep
├── test
│   └── .gitkeep
└── truffle-config.js

Go to the contracts directory. In the directory, create two files: Ownable.sol and DocStamp.sol.

//SPDX-License-Identifier:MIT
// Ownable.sol

pragma solidity ^0.5.0;

contract Ownable {
  address public owner;
  event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

  constructor() public {
    owner = msg.sender;
  }

  modifier onlyOwner() {
    require(msg.sender == owner);
    _;
  }

  function transferOwnership(address newOwner) onlyOwner public {
    require(newOwner != address(0));
    emit OwnershipTransferred(owner, newOwner);
    owner = newOwner;
  }
}

This is an ownable contract. The contract implementation is the following:

• Only an authority can generate a certificate. On contract deployment, the authority is the account that deploys the contract. The authority is the contract owner.

• The contract owner can transfer their authority.

  DocStamp.sol

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  //SPDX-License-Identifier:MIT
  // DocStamp.sol
  
  pragma solidity ^0.5.0;
  
  import './Ownable.sol';
  
  contract DocStamp is Ownable {
    mapping (bytes32 => address) public records;
  
    event CertificateIssued(bytes32 indexed record, uint256 timestamp, bool returnValue);
  
    function issueCertificate(string calldata name, string calldata details) external onlyOwner {
      bytes32 certificate = keccak256(abi.encodePacked(name, details));
      require(certificate != keccak256(abi.encodePacked("")));
      records[certificate] = msg.sender;
      emit CertificateIssued(certificate, block.timestamp, true);
    }
  
    function owningAuthority() external view returns (address) {
      return owner;
    }
  
    function verifyCertificate(string calldata name, string calldata details, bytes32 certificate) external view
     returns (bool) {
      bytes32 certificate2 = keccak256(abi.encodePacked(name, details));
      // are certificates the same?
      if (certificate == certificate2) {
        // does the certificate exist on the blockchain?
        if (records[certificate] == owner) {
          return true;
        }
      }
      return false;
    }
  }
  

This is the main contract. The contract handles the generation and verification of certificates.

• issueCertificate() — generates a certificate by calculating a hash of the student name and details.

  • Can be called only by the owner.
  • Emits a certificate generation event with the timestamp.
  • The issuer puts the certificate on the blockchain by storing it in the global variable records by passing records[certificate] = msg.sender.

• owningAuthority() — returns the address of issuer/authority.

• verifyCertificate() — calculates a hash of the student name and details, and checks if the contract is on the blockchain.

  • Can be called by anyone.

Create 2_deploy_contracts.js in the migrations directory.

var DocStamp = artifacts.require("./DocStamp.sol");

module.exports = function(deployer) {
deployer.deploy(DocStamp);
};

Compile the contracts:

truffle compile

This will compile the contracts and put them in your build/contracts directory in the .json format. If the contract does not compile, check the compiler version in your truffle-config.js file and ensure that your compiler version matches the pragma solidity version of the contract.

Start the development network on your machine:

truffle develop

Without exiting the Truffle console, deploy the contract to the local development network:

truffle(develop)>  migrate

This will deploy the contract to the development network as specified in thetruffle-config.js.

In your Truffle console, create an instance of the deployed contract:

let instance = await DocStamp.deployed()

You can run instance to see the contract object ABI, bytecode, and methods.

Declare the contract owner:

let owner = await instance.owningAuthority()

You can run owner to see the account that deployed the contract and owns the contract.

Issue the certificate:

let result = await instance.issueCertificate("John", "graduate", {from: owner})

This issues the certificate.

Run result.logs to view the full certificate details.

Example output:

logIndex: 0,
  transactionIndex: 0,
  transactionHash: '0xb3ef241d76bd4d3a3d92ad4fd382785589033a4f561baa2895136a3315b3561b',
  blockHash: '0x29343b9fc5b88bb8c85287463a37a00e8fecce36553880365ca5395d9fb18eeb',
  blockNumber: 7,
  address: '0x3113Aa54D455142a254b43b83FB16c18eD30ba33',
  type: 'mined',
  id: 'log_dbbbec7e',
  event: 'CertificateIssued',
  args: Result {
    '0': '0x837e31a66aa8eec0d7adfd41f84175803ddcae69afd451598f2672f652b2c153',
    '1': [BN],
    '2': true,
    __length__: 3,
    record: '0x837e31a66aa8eec0d7adfd41f84175803ddcae69afd451598f2672f652b2c153',
    timestamp: [BN],
    returnValue: true

Note the record value in the output. This is the hash of the certificate values: name and details. You will need this hash to create the contract test later in this tutorial.

Run the certificate verification:

let verify = await instance.verifyCertificate("NAME", "DETAILS", "CERTIFICATE_HASH", {from: owner})

where

• NAME — the student name on the certificate used on the issuing step.
• DETAILS — any details
• CERTIFICATE_HASH — the hash of DETAILS and NAME. You should have received this hash in the record field at the previous step by running result.logs.

Example:

let verified = await instance.verifyCertificate("John", "graduate",
"0x837e31a66aa8eec0d7adfd41f84175803ddcae69afd451598f2672f652b2c153", {from: owner})

Running verify will now print true if there is a match, and false if there is no match.

Navigate to the test directory.

Create a test.js file:

const DocStamp = artifacts.require('./DocStamp.sol')

contract('DocStamp', function(accounts) {
  it('should issue a certificate', async function() {
    const account = accounts[0]

    try {
      const instance = await DocStamp.deployed()
      await instance.issueCertificate("NAME", "DETAILS")
      const authority = await instance.owningAuthority()

      assert.equal(authority, account)
    } catch(error) {
      assert.equal(error, undefined)
    }
  })

  it('should verify a certificate', async function() {
    const account = accounts[0]

    try {
      const instance = await DocStamp.deployed()
      const verified = await instance.verifyCertificate("NAME", "DETAILS", "CERTIFICATE_HASH")

      assert.equal(verified, true)
    } catch(error) {
      assert.equal(error, undefined)
    }
  })
})

where

• NAME — the student name on the certificate used on the issuing step.
• DETAILS — any details
• CERTIFICATE_HASH — the hash of DETAILS and NAME. You should have received this hash in the record field at one of the previous steps by running result.logs.

Example:

const DocStamp = artifacts.require('./DocStamp.sol')

contract('DocStamp', function(accounts) {
  it('should issue a certificate', async function() {
    const account = accounts[0]

    try {
      const instance = await DocStamp.deployed()
      await instance.issueCertificate("John", "graduate")
      const authority = await instance.owningAuthority()

      assert.equal(authority, account)
    } catch(error) {
      assert.equal(error, undefined)
    }
  })

  it('should verify a certificate', async function() {
    const account = accounts[0]

    try {
      const instance = await DocStamp.deployed()
      const verified = await instance.verifyCertificate("John", "graduate",
"0x837e31a66aa8eec0d7adfd41f84175803ddcae69afd451598f2672f652b2c153")

      assert.equal(verified, true)
    } catch(error) {
      assert.equal(error, undefined)
    }
  })
})

Run the test:

truffle test

The test run output should be Passing.

Install HDWalletProvider.

HDWalletProvider is Truffle’s separate npm package used to sign transactions.

Run:

npm install @truffle/hdwallet-provider

Edit truffle-config.js to add:

• HDWalletProvider

• Your Ethereum node access and credentials. Example:

  Javascript

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  const HDWalletProvider = require("@truffle/hdwallet-provider");
  const mnemonic = "misery walnut expose ...";
  
  module.exports = {
   networks: {
      development: {
          host: "127.0.0.1",
          port: 9545,
          network_id: "5777"
      },
      sepolia: {
          provider: () => new HDWalletProvider(mnemonic, "YOUR_CHAINSTACK_ENDPOINT"),
          network_id: 11155111,
          gas: 4500000,
          gasPrice: 10000000000
      }
     }
  };
  

where

• sepolia — any network name that you will pass to the truffle migrate --network command.
• HDWalletProvider — Truffle’s custom provider to sign transactions
• mnemonic — your mnemonic that generates your accounts. You can also generate a mnemonic online with Mnemonic Code Converter. Make sure you generate a 15-word mnemonic.
• YOUR_CHAINSTACK_ENDPOINT — your Chainstack node endpoint. See View node access and credentials and Ethereum tooling.
• network_id — the Ethereum Sepolia testnet network ID: 5.

Run:

truffle migrate --network sepolia

This will engage 2_deploy_contracts.js and deploy the contract to the Ethereum Sepolia testnet as specified in truffle-config.js.