Blockchain introduction Ethereum Đapp – General architecture Đapp – Environment development Đapp – Demo building Auction application

1. How to develop Decentralized App
on Ethereum
Feb-2018
Phi Huynh & Thien Nguyen

2. Follow us on
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3. Agenda
• Blockchain introduction
• Ethereum
• Đapp – General architecture
• Đapp – Environment development
• Đapp – Demo building Auction application

4. Digital Signature

5. Hash
• Arbitrary input
• Same length output
• Unlikely that two inputs
share the same output

6. Blocks

7. Blockchain
• Distributed (Everybody keep their own copy of the ledger)
• Transaction immutability achieved by way of blocks & chaining
• Leverages consensus mechanism for validating the
transactions
• Uses cryptography for trust, accountability, security
• There is no single point of failure

9. Ethereum
• A blockchain app platform that runs smart
contracts

10. Go Ethereum Client
Geth
ÐΞVp2p [TCP, 30303]
> JS API Console
IPC-RPC
WS-RPC [8546]
JSON-RPC [HTTP, 8545]
Disabled by default
Disabled by default

11. Ethereum Network
• Network Id = 1
• Morden: Network Id = 2 (retired)
• Ropsten: Network Id = 3
• Rinkerby: Network Id = 4
• Kovan: Network Id = 42
• Network Id = Asigned
Live Network
Testnet
Private Network

12. Demo
Setup private Ethereum network

13. Setup private Ethereum network
• Install geth https://geth.ethereum.org/downloads/
• Create genesis.json
• Initialize geth node “$ geth init path/to/genesis.json”
• Start geth
• Attach to geth
• JS console
• Create account
• Start mining
https://github.com/devcafevn/ethereum-auction-app/tree/master/private-network

14. Using Ethereum Wallet and MetaMask
Ethereum Wallet MetaMask
You can install the MetaMask add-on in Chrome,
Firefox, Opera
https://github.com/ethereum/mist/releases

15. Ethereum account types
• Has an address
• Controlled by a private key
• Has an address
• No private key
• Holds and run code
External Owned
Account
Contract Account

16. Denominations
Unit Wei Value Wei
wei 1 wei 1
Kwei (babbage) 1e3 wei 1,000
Mwei (lovelace) 1e6 wei 1,000,000
Gwei (shannon) 1e9 wei 1,000,000,000
microether (szabo) 1e12 wei 1,000,000,000,000
milliether (finney) 1e15 wei 1,000,000,000,000,000
ether 1e18 wei 1,000,000,000,000,000,000

17. GAS
• Gas is the unit in which EVM resource usage is measured
• Gas limit (start gas): max amount of gas you willing to spend
• Gas price: price of gas on ether you willing to pay. Miners
decides the minimal acceptable price
Transaction Fee = Gas used * Gas price
Gas used < Gas limit
=> Refund
Gas used > Gas limit
=> Out of gas exception, no change made

18. Dapp development

19. Remix
• https://remix.ethereum.org
• Writing your first smart contract
pragma solidity ^0.4.0;
contract MyAccount {
uint private myBalance;
function MyAccount(uint _myBalance) public{
myBalance = _myBalance;
}
function getBalance() public constant returns(uint){
return myBalance;
}
function add(uint _amount) public returns(uint){
myBalance += _amount;
return myBalance;
}
}

20. Dapp - general architecture
Network

21. Dapp - General architecture 2
Network
DB
Server

22. Demo
Online Auction App

23. Online Auction App
• Everyone can send their bids to
a contract
• The highest current bid is visible
to every one
• At the end of the bidding period
- The highest bid is sent to the
beneficiary
- Other bidders can withdraw their
bids
Source code: https://github.com/devcafevn/ethereum-auction-app
Image source: https://kryptomoney.com/italian-auction-house-now-accepting-payments-
bitcoins/

24. Blockchain Landscape Big Picture
Developer Tools Fin Tech File Storage
Gaming
Social
Digital Asset
Video
Security
And much much more …
SMART CONTRACTS
TOMO
CHAIN

25. Blockchain – Innovation Journey
When the journey began
2008
Adopting Tokenomics
2nd., beyond
currency
Inter organizational
cooperation
3rd., Smart Contracts
PoS, Scaling, on-chain,
off-chain, …
https://hbr.org/2017/02/a-brief-history-of-blockchain

26. Q & A
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27. THANK YOU
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