Web API with node and express used to access a private blockchain.

Table of Contents:

• Prerequisites
• Getting Started
• Running the Application
• Validate Your Wallet Address and Generate Signature
• Validate Message Signature
• Configure Star Registration Endpoint
• Search by Blockchain Wallet Address
• Search by Star Block Hash
• Search by Star Block Height

Prerequisites

If things are acting funky then you need to install the dependencies using NPM

We are using the EXPRESS Framework.

npm install level --save
npm install crypto-js --save
npm install express --save

Getting Started

• Download git repo
• Run node application
• Interact with in browser

Running the Application

In your terminal run the application once you have navigated to the proper package :

node index.js

We can get the data at a specific height with the endpoint :

blockheight is the index of the block we want to retrieve

http://localhost:8000/block/<blockheight>

We post data with the same endpoint :

A new block will only be added to the chain if you include data in the body of the POST request.

http://localhost:8000/block

For both requests, the block will be displayed to the browser window in JSON format :

"{\"hash\":\"d0bf72ce71844ac65aa37849118e81581499b5e3922f6eda1ca0b491a54b1dbd\",\"height\":1,\"body\":\"boss data\",\"time\":\"1537838613\",\"previousBlockHash\":\"b911e16c74f6fb8a63415e4ac98abbc1d26c63438a04148bf5c7775942cd1764\"}"

Validate Your Wallet Address and Generate Signature

Start out by submitting a validation request to an API endpoint:

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

Json Response Example:

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

Generate the signature to be used in the following curl command by opening up the wallet you've been using on the testnet. In my case I used Electrum. Go through the process to sign your message with your 256 bit hash:

Validate Message Signature

Send a validation request:

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="
}'

And you should expect a JSON response similar to this one

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

Configure Star Registration Endpoint

URL This functionality should be provided at the following URL.

http://localhost:8000/block

Payload Wallet address (blockchain identity), star object with the following properties.

Requires address [Wallet address]

Requires star object with properties

right_ascension

declination

magnitude [optional]

constellation [optional]

star_story [Hex encoded Ascii string limited to 250 words/500 bytes]

JSON Response

block object

Example: Block with star object endpoint Post block with curl

curl -X "POST" "http://localhost:8000/block" \
     -H 'Content-Type: application/json; charset=utf-8' \
     -d $'{
  "address": "142BDCeSGbXjWKaAnYXbMpZ6sbrSAo3DpZ",
  "star": {
    "dec": "-26° 29'\'' 24.9",
    "ra": "16h 29m 1.0s",
    "story": "Found star using https://www.google.com/sky/"
  }
}'

JSON Response Example

{
  "hash": "a59e9e399bc17c2db32a7a87379a8012f2c8e08dd661d7c0a6a4845d4f3ffb9f",
  "height": 1,
  "body": {
    "address": "142BDCeSGbXjWKaAnYXbMpZ6sbrSAo3DpZ",
    "star": {
      "ra": "16h 29m 1.0s",
      "dec": "-26° 29' 24.9",
      "story": "466f756e642073746172207573696e672068747470733a2f2f7777772e676f6f676c652e636f6d2f736b792f"
    }
  },
  "time": "1532296234",
  "previousBlockHash": "49cce61ec3e6ae664514d5fa5722d86069cf981318fc303750ce66032d0acff3"
}

Search by Blockchain Wallet Address

Details

Get endpoint with URL parameter for wallet address JSON Response Star block objects URL

http://localhost:8000/stars/address:[ADDRESS]

Payload URL parameter with wallet address.

Example: stars/address:[address] endpoint

Get request with curl

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

Example: JSON response

[
  {
    "hash": "a59e9e399bc17c2db32a7a87379a8012f2c8e08dd661d7c0a6a4845d4f3ffb9f",
    "height": 1,
    "body": {
      "address": "142BDCeSGbXjWKaAnYXbMpZ6sbrSAo3DpZ",
      "star": {
        "ra": "16h 29m 1.0s",
        "dec": "-26° 29' 24.9",
        "story": "466f756e642073746172207573696e672068747470733a2f2f7777772e676f6f676c652e636f6d2f736b792f",
        "storyDecoded": "Found star using https://www.google.com/sky/"
      }
    },
    "time": "1532296234",
    "previousBlockHash": "49cce61ec3e6ae664514d5fa5722d86069cf981318fc303750ce66032d0acff3"
  },
  {
    "hash": "6ef99fc533b9725bf194c18bdf79065d64a971fa41b25f098ff4dff29ee531d0",
    "height": 2,
    "body": {
      "address": "142BDCeSGbXjWKaAnYXbMpZ6sbrSAo3DpZ",
      "star": {
        "ra": "17h 22m 13.1s",
        "dec": "-27° 14' 8.2",
        "story": "466f756e642073746172207573696e672068747470733a2f2f7777772e676f6f676c652e636f6d2f736b792f",
        "storyDecoded": "Found star using https://www.google.com/sky/"
      }
    },
    "time": "1532330848",
    "previousBlockHash": "a59e9e399bc17c2db32a7a87379a8012f2c8e08dd661d7c0a6a4845d4f3ffb9f"
  }
]

Search by Star Block Hash

Get endpoint with URL parameter for star block hash JSON Response

Star block object URL

http://localhost:8000/stars/hash:[HASH]

Payload URL parameter with star block hash.

Example: stars/hash:[hash] endpoint

Get request with curl

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

Example: JSON response

{
  "hash": "a59e9e399bc17c2db32a7a87379a8012f2c8e08dd661d7c0a6a4845d4f3ffb9f",
  "height": 1,
  "body": {
    "address": "142BDCeSGbXjWKaAnYXbMpZ6sbrSAo3DpZ",
    "star": {
      "ra": "16h 29m 1.0s",
      "dec": "-26° 29' 24.9",
      "story": "466f756e642073746172207573696e672068747470733a2f2f7777772e676f6f676c652e636f6d2f736b792f",
      "storyDecoded": "Found star using https://www.google.com/sky/"
    }
  },
  "time": "1532296234",
  "previousBlockHash": "49cce61ec3e6ae664514d5fa5722d86069cf981318fc303750ce66032d0acff3"
}

Search by Star Block Height

Details

Get endpoint with URL parameter for star block height JSON Response Star block object URL

http://localhost:8000/block/[HEIGHT]

Payload URL parameter with block height.

Example: stars/address:[address] endpoint

Get request with curl

curl "http://localhost:8000/block/1"

Example: JSON response

{
  "hash": "a59e9e399bc17c2db32a7a87379a8012f2c8e08dd661d7c0a6a4845d4f3ffb9f",
  "height": 1,
  "body": {
    "address": "142BDCeSGbXjWKaAnYXbMpZ6sbrSAo3DpZ",
    "star": {
      "ra": "16h 29m 1.0s",
      "dec": "-26° 29' 24.9",
      "story": "466f756e642073746172207573696e672068747470733a2f2f7777772e676f6f676c652e636f6d2f736b792f",
      "storyDecoded": "Found star using https://www.google.com/sky/"
    }
  },
  "time": "1532296234",
  "previousBlockHash": "49cce61ec3e6ae664514d5fa5722d86069cf981318fc303750ce66032d0acff3"
}

Author

• Adrian Mohnacs - all da work - github

Acknowledgments

https://classroom.udacity.com/nanodegrees/nd1309/parts/c4ecd959-25d3-46c3-91ba-e5d79c638a34/modules/66945d17-26b1-4370-9b8c-466f4fd3e6ff/lessons/8947cd58-2ad6-486b-8b04-3ae78310ce97/concepts/7f29108d-c59c-4cf6-945a-424dda143e46