Membuat Blockchain Sederhana Dengan NodeJS Dan Crypto

Membuat blockchain sederhana hanya menggunakan nodeJS dan crypto dalam 70 baris code. Crypto merupakan module bawaan dari nodeJS, jadi tidak perlu package module pihak ke-3.

const crypto = require("crypto");

class Block {
  constructor(index, data, prevHash) {
    this.index = index;
    this.timestamp = Math.floor(Date.now() / 1000);
    this.data = data;
    this.prevHash = prevHash;
    this.hash = this.getHash();
  }

  getHash() {
    var encript =
      JSON.stringify(this.data) + this.prevHash + this.index + this.timestamp;
    var hash = crypto
      .createHmac("sha256", "secret")
      .update(encript)
      .digest("hex");

    return hash;
  }
}

class BlockChain {
  constructor() {
    this.chain = [];
  }

  addBlock(data) {
    let index = this.chain.length;
    let prevHash =
      this.chain.length !== 0 ? this.chain[this.chain.length - 1].hash : 0;
    let block = new Block(index, data, prevHash);
    this.chain.push(block);
  }

  chainIsValid() {
    for (var i = 0; i < this.chain.length; i++) {
      if (this.chain[i].hash !== this.chain[i].getHash()) return false;
      if (i > 0 && this.chain[i].prevHash !== this.chain[i - 1].hash)
        return false;
    }
    return true;
  }
}

const blockChain = new BlockChain();
blockChain.addBlock({
  sender: " San Engineer",
  receiver: "Frodo",
  ammount: 100000,
});
blockChain.addBlock({
  sender: "San Developer",
  receiver: "Bagins",
  ammount: 40000,
});

blockChain.addBlock({
  sender: "San Mac",
  receiver: "Rings",
  ammount: 8,
});

// check receiver true or false
blockChain.chain[0].data.receiver = "Frodo";