Hierarchical interac,ons between Ethereum m sma mart contracts - PowerPoint PPT Presentation

Hierarchical interac,ons between Ethereum m sma mart contracts across Te Testnets Yao-Chieh Hu, Ting-Ting Lee, Dimitris Chatzopoulos, Pan Hui yhuag@ust.hk, tleeae@ust.hk, dcab@cse.ust.hk, panhui@cse.ust.hk The Hong Kong University of Science and Technology 1

Background Knowledge • What is Ethereum Blockchain? 2

Background Knowledge • What is Smart Contract? 3

Background Knowledge • Ether(ETH) vs. Gas 4

Background Knowledge • What is Test Networks (testnets)? 5

Background Knowledge • What is a dApp (decentralized applicaRon)? Add a pic of DApp 6

The Problem • Smart contracts cannot share common states • Our proposal: 7

Exis,ng Alterna,ves • Smart Contract Inheritance • Share logic, not data 8

Exis,ng Alterna,ves • Libraries • Share logic, not data 9

Comparison with DApp DApps can access everything on the client Custodian contracts can only access the contracts shared state of the client contracts 10

Use Case - eTickets 11

Use Case • Custodian Contract (movie company) creates client contracts as Rckets 12

Use Case • Alice buys Rcket • Client contract ownership transfers from movie seller to Alice 13

Use Case • Alice sells her Rcket to Bob • Client contract transfers Rcket ownership from Alice to Bob 14

Use Case • Movie Rcket expiring Rme changed • Custodian contract changes the shared variable “ expireTime ” in every client contract 15

Technology Used • Ethereum Blockchain and Solidity • Testnets • Ropsten (196 nodes | PoW) • Rinkeby (49 nodes | PoA) • Kovan (145 nodes | PoA) • MetaMask • The Truffle Framework 16

Experiments • Latency • Deployment • Shared state update • Gas Usage • Deployment • Shared state update 17

Deployment latency 18

Deployment latency per contract Client Contract Deployment EffecRve Latency across testnets 19

Deployment gas usage Client Contract Deployment Gas Usage on Ropsten testnet 20

State muta,on sec Shared state mutaRon latency across Ethereum testnets 21

State muta,on gas usage Shared state mutaRon gas usage on Ropsten testnet 22

Max number of clients that can be mutated at once Maximum batch size of shared state mutaRon across testnets 23

Conclusion • Hierarchical structure of Ethereum smart contract can allow shared states between contracts! 24

Any ques;ons? yhuag@ust.hk 25

Back up Slides 26

Experiments (1) sec Custodian Contract Deployment Latency across Testnets 27

Experiments (2) Custodian Contract Deployment Gas Usage across testnets 28

Experiments (3) sec Client Contract Deployment Total Latency across testnets 29

Experiments (6) sec Shared state mutaRon latency across Ethereum testnets 30

Experiments (7) Shared state mutaRon average latency across Ethereum testnets 31

Experiments (8) Shared state mutaRon gas usage on Ropsten testnet 32

State muta,on per contract Shared state mutaRon average latency across Ethereum testnets 33

Solu,on Breakdown - Architecture 34

Architecture • Custodian contract • Supervise, track and manage Client contracts • Client contract • Only be created from its Custodian contract • Only shared states are externally modifiable 35