This document discusses using Node.js to build blockchain applications. It begins with explaining key blockchain concepts like hashes, Merkle trees, blocks and immutability. It then discusses consensus algorithms like proof-of-work and incentives. Examples are given of Bitcoin, Ethereum and Hyperledger blockchains. Reasons for using Node.js to build blockchain apps are provided, along with examples like BitcoinJS, EthereumJS, smart contracts with Solidity, the Truffle framework, dApps, MetaMask, and Hyperledger Composer. Finally, Blockstack is mentioned and a demo app link is provided.

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C O N F I D E N T I A L
Node.js and Blockchain
Building the Web 3.0 with Node.js

2. October 27, 2017
Julián Duque
Developer and Educator / Community Organizer / Engineer
@julian_duque

3. October 27, 2017
Julián Duque
Not a Crypto Expert / Not here for Crypto Currencies (or ICOs)
@julian_duque

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What is Blockchain?
📦⛓
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Hashes
hash(‘😀’) = 2a02ea…7b6
hash(‘😃’) = e36f86…028
hash(‘Hola’) = f688ae…22e
hash(‘Hola!’) = 0676dc…06f

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Merkle Trees
binary hash tree
Image credit: Wikipedia

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Blockchains
• Continuously growing, append only, list of records
(blocks)
• Distributed Ledger Technology (DLT)
• Linked and secured using cryptography

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Blockchains
Image credit: Wikipedia

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Blockchain Immutability
Image credit: edX - Hyperledger Course

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Reaching Consensus
Proof of Work
• Blocks are added to the ledger gradually
• People (nodes) take turns to add blocks
• Root checksum must start with a number of zeroes (difficulty, conditions)
• Block includes a nonsense (nonce) that can be changed to create new
checksums
• Difficulty is adjusted to target desired time between blocks (control)

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Reaching Consensus
Incentives
• Miner (node) who find a new block gets a reward
• Reward is used as currency and to pay transaction fees
• Miners also get transaction fees along with the reward
• Encourage miners to process blocks with transactions (Game theory)
• Encourage users to pay transaction fees depending on urgency

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Public vs Private
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Bitcoin
• Crypto Currency (BTC)
• Transfer value from address to address (wallet
to wallet)
• Scripting Language - Turing-Incomplete
• Consensus Algorithm: Proof of Work

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Ethereum
• Virtual Machine (EVM)
• Usage is metered by transaction fees (gas)
• Crypto Currency (ether - ETH)
• Transactions manipulate state
• EVM is Turing-Complete
• Consensus Algorithm: Proof of Work, moving to Proof
of Stake

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Hyperledger
• Umbrella of Open Source projects
• Focused on Business / Permissioned Blockchains
• No crypto currency
• Consensus algorithms: Depending of Project (PoET,
PFBT)
• Some projects are EVM compatible, others have they
own VM

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Why Node.js?
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Why Node.js?
• JavaScript: Language of the web
• Great for building tools
• Great as API / Frontend layer

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Develop Blockchain Applications
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BitcoinJS
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BitcoinJS
https://bitcoinjs.org
• Create / Interact with Bitcoin wallets
• Transactions
• Crypto operations

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EthereumJS
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EthereumJS
https://ethereumjs.github.io
• Collection of libraries and utilities for
Ethereum
• Always looking for contributors

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Smart Contracts
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Smart Contracts
• Applications that can be deployed to the
Blockchain (Ethereum / Hyperledger)
• Takes care of State in Blockchain
• Defines and enforces the rules and
penalties around an agreement

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Solidity
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Solidity
• High level language to build Smart
Contracts for Ethereum
• Typed Language
• Based on JavaScript
• Compiled to EVM

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Solidity
pragma solidity ^0.4.11;
contract HelloWorld {
uint public balance;
address public owner;
function HelloWorld() public {
owner = msg.sender;
balance = 0;
}
function update() public payable isOwner() {
balance = msg.value;
}
modifier isOwner() {
require(msg.sender == owner);
_;
}
}

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Solidity
$ npm install -g solc

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Truffle
• Framework to build, test and deploy
Smart Contracts
• Test Smart Contracts with JavaScript
• Project generators for ĐApps

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Truffle
$ npm install -g truffle

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ĐApps
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ĐApps
https://www.stateofthedapps.com
• Web 3.0 - Decentralized Applications
• Interact with Smart Contracts using backend-
less JavaScript Applications
• Bitcoin: The first ĐApp

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MetaMask
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MetaMask
https://www.metamask.io
• Brings Ethereum to your Browser
• Perfect for running ĐApps
• No need to have a full node running

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Hyperledger Composer
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Hyperledger Composer
https://hyperledger.github.io/composer/
• Build private Blockchain Applications and Business Networks
• Build Smart Contracts with a model language
• Generate REST APIs
• Node.js modules (composer-client) to interact with your network

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Blockstack
https://blockstack.org
• Build decentralized applications with JavaScript (BlockstackJS)
• Virtualchain: An existing Blockchain extension

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Demo
https://julianduque.github.io/simple-vote/
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Thank you!
Julián Duque
julian@nodesource.com
@julian_duque