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
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
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
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