intro to smart contract on blockchainen

• How to perform : self-enforcing , self executing• Smart Contract in real-life： service?. smart contract on blockchain... • its totally up to you • reach an agreement with untrustful pa

SMART CONTRACT

林修平

• buying, selling, renting, leasing, insurance, investment, etc

• actively or inactively perform

“SMART” CONTRACT

• How to perform : self-enforcing , self executing

• Smart Contract in real-life：

service?

“SMART” CONTRACT

smart contract on blockchain

• What differences does it make?

• or program and mathematics?

• its totally up to you

• reach an agreement with untrustful party

smart contract on blockchain

• https://www.thenewslens.com/article/11796

• a washing machine that can buy detergent itself if needed

• without blockchain

• cash flow :

• online payment -> companies that sells detergent -> transportation companies

• what’s the cost?

• time, efforts on checking status and verify

• what if something went wrong?

• how long does it take to find out the problem?

• who will find out the problem?

• how long do I have to wait?

smart contract on blockchain

• https://www.thenewslens.com/article/11796

• a washing machine that can buy detergent itself if needed

• with blockchain

• cash flow :

• online payment -> companies that sells detergent -> transportation companies

• what’s the cost?

• transaction fee

• what if something went wrong?

• how long does it take to find out the problem?

• who will find out the problem?

• how long do I have to wait?

smart contract on blockchain

BLOCKCHAIN + IOT

• how to make sure what it says is true?

• share same information

• distributed?

• can an IOT device provide such capability in its storage unit?

• decentralized?

BLOCKCHAIN + IOT?

• main problems in IOT

BLOCKCHAIN + IOT?

CHALLENGE

• External Information

• Liquidity

• has no control beyond ledgers

• say you start a bet on tomorrow’s game score…

• how do you provide the score to smart contract?

• fetch the source from outside?

• which source to trust?

• can everyone fetch from the same source?

• will it expire? disappear? change from time to time?

• for now, smart contracts on blockchain can not fetch external information itself

• provided by third party

company, is the money you pay monthly going to stay in there indefinitely?

out of the money which means the money will only be

• Liquidity

Ethereum smart contract

Ethereum smart contract

Ethereum smart contract

• each operation has a price(gas)

• pay for gas where user decides how much to pay per unit gas

• pay with ether

Ethereum smart contract

• 1 write your contract

Ethereum smart contract

• 1 write your contract

• 2 compile it to byte code

Ethereum smart contract

• 1 write your contract

• 2 compile it to byte

code

mined

Ethereum smart contract

• 1 write your contract

Ethereum smart contract

Ethereum smart contract

• 1 write your contract

• 2 compile it to byte code

https://ethereum.github.io/browser-solidity/

ethereum/wiki/Building-Ethereum

https://github.com/ethereum/go-https://github.com/ethereum/mist/releases

living example : DAO

• Decentralized Autonomous Organization

• by slock.it

living example : DAO

• Recursive calling vulnerability

• propose a split -> execute the split -> withdraw

• propose a split -> execute the split -> propose a split ->

living example : DAO

problem1

problem2

living example : DAO

problem1

living example : DAO

problem1

• address.call.value(amount)

• supply with enough gas

• if address refers to a contract, it triggers fallback function

• do what whatever you want as long as enough gas remaining

living example : DAO

problem2

living example : DAO

living example : DAO

• votes for hard fork