Blockchain notary web service application

The goal of the project was to create a blockchain notary service that validates users before it allows them to make requests for storing assets attributed to their ownership. The application features a RESTful web API with multiple GET and POST endpoints on a local server through which users can interact with the blockchain solution backend.

Procedure implemented in application

The application implements the following logical flow:

Structure of application

• app.js: central file (to be executed for utilization of project); initializes API framework (based on express.js), imports required classes and initiates blockchain backend operation.
• Block.js: implements a simple data model for the Block class
• BlockChain.js: implements a simple blockchain (one transaction per block) with the necessary methods
• memPool.js: implements a MemPool component for the temporary storage and support of items to be validated
• LevelSandbox.js: data access layer of the app; ensures that data added to the blockchain is stored persistently on the hard drive
• BlockController.js: implements the required GET and POST endpoints by importing the necessary classes from the other files and linking methods to the corresponding endpoints

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes.

Prerequisites and installing

To install the software, you need to do the following:

1. Install Node.JS on your computer - visit https://nodejs.org/en/ and choose installer for your system

2. Clone or download GitHub repo files into desired directory from https://github.com/realtamas/blockchain-notary-web-service

3. Initialize node.js project in directory where files are located:

npm init -y

4. Install and save dependencies (crypto-js, level, express, body-parser) to project folder:

npm install crypto-js --save
npm install level --save
npm install express --save
npm install body-parser --save
npm install bitcoinjs-message --save
npm install bitcoinjs-lib --save
npm install hex2ascii --save

Running and testing the application

1. Run app.js from project directory:

node app.js

• app.js will initialize local server with GET and POST endpoints, listening on port 8000 (http://localhost:8000)
• blockchain application (Block.js, Blockchain.js, LevelSandbox.js, memPool.js and Blockcontroller.js) will initialize a blockchain with a Genesis Block and 9 Test Blocks (data persists in LevelDB local database)

2. Test basic GET and POST endpoints:

• POST request should include a json object with the desired block body contents (block.time, block.hash, block.previoushash will be added automatically by application), should include "Content-Type: application/json" in header, e.g.:

  curl --header "Content-Type: application/json" --request POST -i --data '{"body":"Test Block"}' http://localhost:8000/api/block
  # this will add a new block to the end of the blockchain and return the contents of the new block in json format

• GET request can be parametrized with api/block/:index, for example:

  curl --request GET -i http://localhost:8000/api/block/1  # will return Block #1 from blockchain

3. Test validation and star registry functionality:

• Submit an address validation request:

  # sample data
  curl -X POST http://localhost:8000/requestValidation \
  -H 'Content-Type: application/json' \
  -H 'cache-control: no-cache' \
  -d '{
      "address":"19xaiMqayaNrn3x7AjV5cU4Mk5f5prRVpL"
      }'

  The app will add the request to the MemPool (temporary storage for requests to be validated) and sets a timeout of 5 minutes for validation. Message to be validated will be returned in the response from the API (sample data):

  {
  "walletAddress": "19xaiMqayaNrn3x7AjV5cU4Mk5f5prRVpL",
  "requestTimeStamp": "1541605128",
  "message": "19xaiMqayaNrn3x7AjV5cU4Mk5f5prRVpL:1541605128:starRegistry",
  "validationWindow": 300
  }

• Use your Electrum wallet to sign the message and post the signature with the address:

  # sample data
  curl -X POST http://localhost:8000/message-signature/validate \
  -H 'Content-Type: application/json' \
  -H 'cache-control: no-cache' \
  -d '{
      "address":"19xaiMqayaNrn3x7AjV5cU4Mk5f5prRVpL",
      "signature":"H8K4+1MvyJo9tcr2YN2KejwvX1oqneyCH+fsUL1z1WBdWmswB9bijeFfOfMqK68kQ5RO6ZxhomoXQG3fkLaBl+Q="
      }'

  The app will validate the signature using bitcoinjs-message and if the signature is valid, will put the requestor's wallet address as identifier into the MemPoolValid temporary storage. The app will return the validRequest object (sample data):

  {
  "registerStar": true,
  "status": {
      "address": "19xaiMqayaNrn3x7AjV5cU4Mk5f5prRVpL",
      "requestTimeStamp": "1541605128",
      "message": "19xaiMqayaNrn3x7AjV5cU4Mk5f5prRVpL:1541605128:starRegistry",
      "validationWindow": 200,
      "messageSignature": true
  }

}

• Send star data to be stored:

  curl -X POST http://localhost:8000/message-signature/validate \
  -H 'Content-Type: application/json' \
  -H 'cache-control: no-cache' \
  -d '{
      "address": "19xaiMqayaNrn3x7AjV5cU4Mk5f5prRVpL",
      "star": {
              "dec": "68° 52' 56.9",
              "ra": "16h 29m 1.0s",
              "story": "Found star using https://www.google.com/sky/"
      }
      }'

  The app will verify that the sender's wallet address in included among already validated requests. If so, it will add the star data to the blockchain for permanent storage.

4. Test additional functionality:

• Getting star blocks by hash (sample hash):

  curl http://localhost:8000/stars/hash/a59e9e399bc17c2db32a7a87379a8012f2c8e08dd661d7c0a6a4845d4f3ffb9f

• Getting star blocks by wallet address (all star blocks assigned to given wallet address) - sample address:

  curl http://localhost:8000/stars/address/142BDCeSGbXjWKaAnYXbMpZ6sbrSAo3DpZ

• Getting star blocks by height (logically the same as the other getBlockByHeight method, but due to technical reasons I created a seperate route for this one):

  curl http://localhost:8000/block/2

Built With

• Node.JS - The JavaScript runtime used
• Express.JS - The web API framework used
• LevelDB - Used to persist blockchain data on disk
• Electrum Wallet - Used to generate signatures
• Postman - Used for API endpoint testing
• MS Visual Studio Code - Code editor used for scripting

Authors

• Tamas Dinh LinkedIn profile