An Introduction to Ethereum and Smart Contracts

Contents

1. Special Thanks 3
2. Foreword 4
3. Bitcoin and The Blockchain 5
   1. Bitcoin and the Double-Spending Problem 5
   2. The Blockchain 7
      1. Validating Transactions 8
      2. Ordering Transactions 11
         1. Physics to the Rescue 14
      3. Definition 17
   3. Example: a Perpetual Message System Using Webtasks and Bitcoin 20
      1. The implementation 21
         1. The /new endpoint 21
         2. The /address endpoint 21
         3. The /message endpoint 21
         4. The /debugNew endpoint 22
      2. The Code 22
      3. Deploying the example 24
   4. Summary 25
4. Ethereum: a Programmable Blockchain 26
   1. Introduction 26
      1. Blockchain Recap 26
   2. Ethereum: a Programmable Blockchain 28
      1. Ether 31
      2. Smart Contracts 31
         1. State 32
         2. History 35
         3. Solidity and a Sample Smart Contract 36
      3. Current and Potential Uses 37
         1. The Decentralized Autonomous Organization (DAO) 38
         2. A Central Bank or Your Own Coin 38
         3. A Crowdfunding System 38
         4. Prove That You Said Something in the Past 39
         5. Proof of Existence for Digital Assets 39
   3. Example: A Simple Login System using Ethereum 40
      1. Running the Example 44
         1. Get an Ethereum node client 44
         2. Create a new Ethereum account to mine some Ether 44
         3. Start mining some Ether 45
         4. Compile and deploy our Login contract 45
         5. Install an Ethereum wallet 46
         6. Tell the Ethereum wallet of the contract 46
         7. Deploy the backend 49
         8. Serve the frontend 49
         9. Test everything together! 50
   4. Summary 50
5. A Practical Authentication Solution for Ethereum Users 51
   1. Introduction 51
   2. Towards a Practical Authentication Solution for Ethereum Users 52
   3. A Login System for Ethereum Users 53
      1. Registration 57
      2. Authentication 59
      3. Cons 60
   4. Try it out! 60
      1. Get an Ethereum Wallet 61
         1. Get Metamask 61
         2. Create a New Account 61
         3. Get Some Ether 61
      2. Get the Mobile Authenticator App 62
         1. Get the App 62
         2. Register 62
      3. Enable Your Ethereum Address for Logins 62
         1. Get Your Mobile App (Secondary) Address 62
         2. Call the Contract! 63
      4. Login to Our Test Site 64
      5. Explore the Code 64
   5. Summary 65