What is a decentralised application ? - Les Jeudis du Libre
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A decentralized application (DApp) is an application that runs on a decentralized network like Ethereum rather than being hosted and controlled by a single company. A DApp uses blockchain technology and smart contracts to allow peer-to-peer transactions and decisions without an intermediary. Ethereum allows developers to create DApps with Turing-complete smart contracts that can automate processes and disintermediate industries like banking, insurance, and more. DApps are accessed through a web interface or mobile app and interact with smart contracts deployed on the Ethereum blockchain.
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What is a decentralised application ? - Les Jeudis du Libre
- 1. What is a Decentralised application? Said Eloudrhiri 1 Les Jeudis du Libre November 15th 2018
- 2. 2 •In IT since 1992 •ScrumMaster, Agile coach •Trainer, Speaker •Founder of Noratek •Co-organiser of the Wajug •Co-founder of ChainSkills @eloudsa
- 3. 3 Disclaimer • We are not related to any bank or trading company. • Material used in this presentation remains the property of their owners.
- 6. What the @#!! is the Blockchain? 6
- 7. 7
- 8. 8
- 9. 9
- 10. Once upon a time… 10
- 20. A few months later… 15
- 26. 16 1GeXY... 13ZC… min(s) Decentralized - Distributed - Immutable - Public Public: Private:141497… Public: Private: 35725…
- 27. Bloc #0 Bloc #1 Bloc #2 Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX n TX 3 17
- 28. Bloc #0 Bloc #1 Bloc #2 Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 17
- 29. Bloc #0 Bloc #1 Bloc #2 Bloc #3 Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 17
- 30. Bloc #0 Bloc #1 Bloc #2 Bloc #3 Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 17 TX 3 Tx 3 0x123 sent 1 BTC to 0x456
- 31. Mining par PoW 18 1GeXY... 13ZC…Public: Public:
- 32. Mining par PoW 18 1GeXY... 13ZC…Public: Public:
- 33. Mining par PoW 18 1GeXY... 13ZC…Public: Public:
- 34. Mining par PoW 18 1GeXY... 13ZC…Public: Public:
- 35. Mining par PoW 18 1GeXY... 13ZC…Public: Public:
- 36. Mining par PoW 18 1GeXY... 13ZC…Public: Public:
- 37. Mining par PoW 18 1GeXY... 13ZC…Public: Public:
- 38. Mining par PoW 18 1GeXY... 13ZC…Public: Public:
- 41. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1
- 42. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1
- 43. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1 TX 3 fake
- 44. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1 TX 3 fake
- 45. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1 TX 3 fake
- 46. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1 TX 3 fake
- 47. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1 TX 3 fake
- 48. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1 TX 3 fake
- 49. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1 TX 3 fake …
- 50. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1 TX 3 fake …
- 51. Bloc #0 Bloc #1 Bloc #n Bloc #n+x Genesis TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n TX 1 TX 2 TX 3 TX n 20 … TX 1 TX 2 TX n TX 3 … Bloc #n-1 TX 3 fake …
- 52. #chainskills Blockchain Bitcoin 21 • From Internet of Information to Internet of Value • Distributed and decentralised network • Immutable distributed ledger • cryptocurrency • Military grade encryption • Consensus algorithm • No double spent • Anonymity • Transparency • Trust in trustless network
- 53. Bitcoin is digital currency 22
- 55. Monetary transaction 24 1GeXY... 13ZC…Public: Public:
- 56. Monetary transaction 24 1GeXY... 13ZC…Public: Public: if(balance(1GeXY…) > amount) { balance(1GeXY…) -= amount; balance(13ZC…) += amount; }
- 57. Then comes Ethereum … 25
- 59. What does it bring? • Generalized transactions • Each node is a virtual machine • Turing-complete language • Worldwide computer • Better performance and evolutivity • PoW consensus algorithm with rewards • A new crypto-currency with intrinsic value (Ether) 27
- 61. Disintermediation • What Bitcoin did for the banks, generic platforms like Ethereum can do it for every single intermediary-based industry • Notaries, insurance, energy, recruitment, government, administration, transportation, Predictions markets, liquid democracy, etc • Reinvent existing applications • Create new applications that were simply not relevant before 29
- 63. In Ethereum, business processes are coded into (immutable) smart contracts 31
- 64. In Ethereum, business processes are coded into (immutable) smart contracts 31
- 65. In Ethereum, business processes are coded into (immutable) smart contracts 31
- 68. Smart contract 32 • Micro-service • immutable
- 69. Smart contract 32 • Micro-service • immutable • state variables
- 70. Smart contract 32 • Micro-service • immutable • state variables • functions modify state variables
- 71. Smart contract 32 • Micro-service • immutable • state variables • functions modify state variables • balance in ether
- 72. Smart contract 32 • Micro-service • immutable • state variables • functions modify state variables • balance in ether • distributed in the network
- 73. Smart contract 32 • Micro-service • immutable • state variables • functions modify state variables • balance in ether • distributed in the network • uniquely identified through its address
- 74. Smart contract 32 • Micro-service • immutable • state variables • functions modify state variables • balance in ether • distributed in the network • uniquely identified through its address • send ether to a user or another contract
- 75. Smart contract 32 • Micro-service • immutable • state variables • functions modify state variables • balance in ether • distributed in the network • uniquely identified through its address • send ether to a user or another contract • contract can collaborate with another contract
- 76. Smart contract 32 • Micro-service • immutable • state variables • functions modify state variables • balance in ether • distributed in the network • uniquely identified through its address • send ether to a user or another contract • contract can collaborate with another contract • emit events or throw exceptions
- 79. 34 Bloc 0 Bloc 1 Bloc 2 Bloc 3 Bloc n Ethereum Virtual Machine 0x123
- 80. 34 Bloc 0 Bloc 1 Bloc 2 Bloc 3 Bloc n smart contract Ethereum Virtual Machine 0x123 ?
- 82. 36 HTML, CSS, JS web3js Dapp/Frontend Bloc 0 Bloc 1 Bloc 2 Bloc 3 Bloc n smart contract Dapp/BackendEthereum Virtual Machine 0x123 wrapper Wallet
- 83. Deploy a smart contract pragma solidity ^0.4.25; contract Greetings { string message; constructor() public { message = "I am ready!"; } function setGreetings(string _message) public { message = _message; } function getGreetings() public view returns (string) { return message; } } Solidity code Greetings.sol Bytecode ABI Address Code Balance Greetings.json Ethereum node compile deploy
- 84. 38 0X123… 0x456… Transaction fee (Gas) 21000 Gas
- 87. Gas, Gas Price 40 Transaction Fee = Gas * Gas Price 0X123… 0x456… Gas: sum used to execute each opcode Gas Price: Price in Wei that the account is willing to pay per unit of gas
- 89. Gas, Gas Price 42 Transaction Fee = Gas * Gas Price 0X123… 0x456… ? Gas: 21000 Gas Price: 20 Gwei
- 90. Gas, Gas Price 42 Transaction Fee = Gas * Gas Price 0X123… 0x456… ? Gas: 21000 Gas Price: 20 Gwei Defined by you Opcode cost
- 91. Gas, Gas Price 43 Transaction Fee = Gas * Gas Price 0X123… 0x456… Transaction Fee = 420000 Gwei or 0.00042 Ether Alice paid = 1.00042 ETH
- 92. Gas, Gas Price 43 Transaction Fee = Gas * Gas Price 0X123… 0x456… Transaction Fee = 420000 Gwei or 0.00042 Ether Alice paid = 1.00042 ETH 1 ETH
- 93. Gas, Gas Price 43 Transaction Fee = Gas * Gas Price 0X123… 0x456… Transaction Fee = 420000 Gwei or 0.00042 Ether Alice paid = 1.00042 ETH Paid by Alice to the Miner 1 ETH
- 94. Price too low 44 Transaction Fee = Gas * Gas Price 0X123… 0x456… Gas: 21000 Gas Price: 1 Gwei
- 95. Price too low 44 Transaction Fee = Gas * Gas Price 0X123… 0x456… Gas: 21000 Gas Price: 1 Gwei Too low? You will have to wait for a miner
- 96. Price too low 44 Transaction Fee = Gas * Gas Price 0X123… 0x456… ? Gas: 21000 Gas Price: 1 Gwei Too low? You will have to wait for a miner
- 98. Read the node = Free 46 0x456… getBalance() getGreetings() getArticlesToSale()
- 99. Interactions 47
- 100. 48 EOA EOA EOA: External Owned Account
- 101. 48 EOA EOA EOA: External Owned Account
- 102. 49
- 103. 49 0x5E9
- 104. 5050
- 105. 5050
- 106. 5151
- 107. 5151
- 108. 5252
- 109. 5252
- 110. Immutability 53
- 111. 5454 Main network
- 112. 5555 Main network
- 113. 5656 Main network
- 114. 5757 Main network
- 115. 5858 Main network
- 116. 59 0x5E9
- 117. 59 0x86C 0x5E9
- 119. 61 Test networks Ropsten (public) Rinkeby (public) Kovan (public) Local test node Fake ETH
- 120. 61 Test networks Ropsten (public) Rinkeby (public) Kovan (public) Local test node Fake ETH
- 121. 62 Upgrade your smart contract
- 122. Tokens 63
- 123. Tokens 64
- 124. Tokens 64 • ether: cryptocurrency of ethereum
- 125. Tokens 64 • ether: cryptocurrency of ethereum • ERC20: fungible tokens
- 126. Tokens 64 • ether: cryptocurrency of ethereum • ERC20: fungible tokens • ERC721: non-fungible tokens
- 127. Usage of a fungible token 65 • Create alternative currency without mining but minting • Speculative token vs Utility token • Exchange platform (DEX) • Initial Coin Offerings • https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
- 128. non-fungible (ERC-721) 66 • Tokens of different value • To represent real value • Art, certificate, property title, patent, etc. • Popular with the game CryptoKitties • http://erc721.org/
- 131. Blockchain = design pattern #chainskills 69
- 132. You need a decision model http://bit.ly/2eLiGCh 70
- 133. You need a decision model http://bit.ly/2eLiGCh 70
- 134. You need a decision model http://bit.ly/2eLiGCh 70
- 135. You need a decision model http://bit.ly/2eLiGCh 70
- 136. You need a decision model http://bit.ly/2eLiGCh 70
- 137. You need a decision model http://bit.ly/2eLiGCh 70
- 141. Distributed consensus is slower VISA (2000) Paypal (115) Bitcoin (7) Ethereum (20) 73
- 142. Transaction confirmation times are long Bitcoin (6 blocks x 600s) Ethereum (12 blocks x 17s) REST (~500ms) 74
- 143. The code is the Law 75 But the Law is the Law
- 144. Thou shall not alter your ledger… EVER! 76
- 145. Ignore it or Use it 77
- 146. 78
- 147. 78
- 148. 79
- 151. #chainskills Disclaimers 81 • Murphy’s Law: if the demo has to fail during a talk, it will fail
- 152. #chainskills Disclaimers 81 • Murphy’s Law: if the demo has to fail during a talk, it will fail • This is completely original code
- 153. #chainskills Disclaimers 81 • Murphy’s Law: if the demo has to fail during a talk, it will fail • This is completely original code • Bear with us: there are PoCs, it might not be the most efficiently coded
- 154. #chainskills Disclaimers 81 • Murphy’s Law: if the demo has to fail during a talk, it will fail • This is completely original code • Bear with us: there are PoCs, it might not be the most efficiently coded • This is by no means usable in production
- 155. #chainskills Disclaimers 81 • Murphy’s Law: if the demo has to fail during a talk, it will fail • This is completely original code • Bear with us: there are PoCs, it might not be the most efficiently coded • This is by no means usable in production • We will focus on smart contracts and show you a bit of web user interface at the end
- 156. #chainskills Disclaimers 81 • Murphy’s Law: if the demo has to fail during a talk, it will fail • This is completely original code • Bear with us: there are PoCs, it might not be the most efficiently coded • This is by no means usable in production • We will focus on smart contracts and show you a bit of web user interface at the end • Room for improvement? Please contribute on Github ;-)
- 160. #chainskills Our demo 84 • Compile and deploy the contract to Ganache using Truffle
- 161. #chainskills Our demo 84 • Compile and deploy the contract to Ganache using Truffle • Interact with the contract through the Truffle console
- 162. #chainskills Our demo 84 • Compile and deploy the contract to Ganache using Truffle • Interact with the contract through the Truffle console • Read the initial greetings message
- 163. #chainskills Our demo 84 • Compile and deploy the contract to Ganache using Truffle • Interact with the contract through the Truffle console • Read the initial greetings message • Change the greeting message
- 164. #chainskills Our demo 84 • Compile and deploy the contract to Ganache using Truffle • Interact with the contract through the Truffle console • Read the initial greetings message • Change the greeting message • Check balances, blocks and transactions on Ganache
- 168. Solidity 88 https://solidity.readthedocs.io/en/latest/ “Solidity is an object-oriented, high-level language for implementing smart contracts. Smart contracts are programs which govern the behaviour of accounts within the Ethereum state.”
- 169. web3.js 89 “web3.js is a collection of libraries which allow you to interact with a local or remote ethereum node, using a HTTP or IPC connection.” https://web3js.readthedocs.io/en/1.0/
- 171. #chainskills PoC: Depositum React + Drizzle + IPFS + ERC-20 91
- 172. #chainskills Store and sell my assets 92
- 173. #chainskills Store and sell my assets 92
- 174. #chainskills Store and sell my assets 92 • Buy some ERC-20 tokens to deposit an asset
- 175. #chainskills Store and sell my assets 92 • Buy some ERC-20 tokens to deposit an asset • Deposit, edit or remove an asset
- 176. #chainskills Store and sell my assets 92 • Buy some ERC-20 tokens to deposit an asset • Deposit, edit or remove an asset • Store the file off-chain on IPFS
- 177. #chainskills Store and sell my assets 92 • Buy some ERC-20 tokens to deposit an asset • Deposit, edit or remove an asset • Store the file off-chain on IPFS • Sell the asset on a marketplace
- 178. #chainskills Store and sell my assets 92 • Buy some ERC-20 tokens to deposit an asset • Deposit, edit or remove an asset • Store the file off-chain on IPFS • Sell the asset on a marketplace • Purchase the asset
- 179. #chainskills Store and sell my assets 92 • Buy some ERC-20 tokens to deposit an asset • Deposit, edit or remove an asset • Store the file off-chain on IPFS • Sell the asset on a marketplace • Purchase the asset • Refund the purchase
- 180. #chainskills Store and sell my assets 92 • Buy some ERC-20 tokens to deposit an asset • Deposit, edit or remove an asset • Store the file off-chain on IPFS • Sell the asset on a marketplace • Purchase the asset • Refund the purchase • Encrypt the file
- 181. #chainskills Store and sell my assets 92 • Buy some ERC-20 tokens to deposit an asset • Deposit, edit or remove an asset • Store the file off-chain on IPFS • Sell the asset on a marketplace • Purchase the asset • Refund the purchase • Encrypt the file • Transfer earning (from tokens sale) to the contract owner
- 182. #chainskills 93 HTML, CSS, JS, React, Drizzle web3js Dapp/Frontend Dapp/Backend AssetContract off-chain
- 187. Solidity 98 https://solidity.readthedocs.io/en/latest/ “Solidity is an object-oriented, high-level language for implementing smart contracts. Smart contracts are programs which govern the behaviour of accounts within the Ethereum state.”
- 188. web3.js 99 “web3.js is a collection of libraries which allow you to interact with a local or remote ethereum node, using a HTTP or IPC connection.” https://web3js.readthedocs.io/en/1.0/
- 189. Drizzle (with React.js and Redux) 100 https://truffleframework.com/drizzle
- 193. And now? 104
- 194. A few Dapps 105
- 195. #chainskills 106
- 196. ChainSkills 107 • Online training on Udemy • 12000+ students • 145 countries • rating: 4,5 on 5 • training.chainskills.com • Target • Managers • Developers • ProofOfCast.com
- 197. ChainSkills 107 • Online training on Udemy • 12000+ students • 145 countries • rating: 4,5 on 5 • training.chainskills.com • Target • Managers • Developers • ProofOfCast.com PROMO CODE: LESJEUDIS
- 198. Thank you 108 @chainskills, @sarbogast, @eloudsa https://www.chainskills.com