Trapdoor Functions

Hashing

Public Key Cryptography

Diffie-Hellman

Signing

Encryption

Merkle Trees

Alice

Bob

A Hunting Game

On Distributed Communication Networks - Paul Baran

Bitcoin vs bitcoin

Why you should care, today.

1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2

Strengths

• it works. today. right now.
• global reach
• objective inference
• inexpensive and swift
• irreversible transactions
• consensus and security
• psuedonymous

Bitcoin Origins

https://bitcoin.org/bitcoin.pdf

Then 2013 Happened

But...what is the blockchain?

Wallets do not hold your bitcoin

• it works. today. right now.
• global reach
• objective inference
• inexpensive and swift
• irreversible transactions
• consensus and security
• psuedonymous

Part 2 - Ethereum and Smart Contracts

Ethereum

What if we put code...

on the blockchain?

The (technical) Advancements of Ethereum

• Turing-completeness- especially loops
• Fine grained value manipulation
• State and multistage contracts
• Blockchain awareness- nonce, the timestamp and previous block hash, etc. should be available

The (interesting) Advancements of Ethereum

https://github.com/ethereum/wiki/wiki/White-Paper#applications

• Types https://solidity.readthedocs.io/en/develop/types.html -just skim this

• constructors and functionshttps://solidity.readthedocs.io/en/develop/structure-of-a-contract.html#functions

special solidity calls https://solidity.readthedocs.io/en/develop/units-and-global-variables.html#special-variables-and-functions -just skim this

Types

• boolean
  • true or false
• int and uint
  • represent 256 bit signed and unsigned numbers respectively
• address
  • holds a 20 byte ethereum address
• bytes1 - bytes32
  • fixed size byte array
• struct
  • fixed size byte array
• enum
  • fixed size byte array

Contract Structure

pragma solidity ^0.4.0;

contract SimpleStorage {
    uint storedData;

  function SimpleStorage() {
    // ...
  }

  function bid() payable { // Function
    // ...
    }

  }

}

Special Operations

• msg.sender
  • the ethereum address that directly called the contract
• msg.value
  • value of the calling transaction
• block.number
  • current blocknumber
• sha256 and sha3
  • hash functions
• selfdestruct(<address>)
  • kill self and send money to an address
• wei, finney, szabo, ether
  • currency denominations

Contract walkthrough

https://tinyurl.com/ycbs6zz6

remix.ethereum.org

Solidity Tutorial Video

After the break

• Web3 - https://github.com/ethereum/wiki/wiki/JavaScript-API#web3eth

• Ganache-cli - https://github.com/trufflesuite/ganache-cli

Part 3 - Tests

Recap

• cryptographic primitives
• history of bitcoin/blockchain
• how to write and deploy smart contracts

Build an Application

Write a contract that allows people to register for arbitrary names

Designing the contract

• How much should a name cost?
• Should people be able to resell their name?
• How long should the name be assigned to a person?
• Can the owner of the contract take names back from buyers?
• How can we keep track of the real world identity of buyers?

https://tinyurl.com/eip20g

Testing

Installation

• NodeJS https://nodejs.org/en/download/
• Truffle - https://github.com/trufflesuite/truffle
• Ganache-cli - https://github.com/trufflesuite/ganache-cli

https://github.com/trufflesuite/truffle-init-default

Mocha

describe('Array', function() {

  before(function() {
    // runs before all tests in this block
  });  

  describe('#indexOf()', function() {
    it('should not be empty', function() {
      // ...some assertions here
    });
  });
});

Mocha

$ ./node_modules/mocha/bin/mocha

  Array
    #indexOf()
      ✓ should not be empty


  1 passing (9ms)

Embark + Mocha

contract('MySimpleContract', function() {

  describe('setting the state', function() {
    // ..some assertions here
  });


  // ...some more contract tests here

});

Chai - expect style

expect(2).to.equal(2);

expect({a: 1, b: 2})
  .to.not.have.any.keys('c', 'd');

expect([1, 2]).to.be.an('array')
 .that.does.not.include(3);

expect(false, 'nooo why fail??').to.be.true;

Part 4

Recap

• cryptographic primitives
• history of bitcoin/blockchain
• setting up an ethereum wallet
• how to write and deploy smart contracts

Limitations of the Blockchain

http://blockchain-guide.readthedocs.io/en/latest/limitations.html

MedRec

Web Dev Intro

More Stuff

Proof of Stake and Authority

Context of Smart Contracts

Race to Empty

 Blockchain Projects

Contact