A Developer Primer on Blockchain

Come find out how you can build a peer-to-peer distributed ledger forged by consensus. Understand through code how to create “smart contracts” and develop a different type of transactional application that establishes trust, accountability and transparency, while streamlining business processes and legal constraints.

Transcript

1. Martin Beeby - @thebeebs PRIMER ON BLOCKCHAIN A DEVELOPER
2. Martin Beeby @thebeebs Software developer Since I was 16 Joined Oracle 5 months ago MARTIN BEEBY
3. Martin Beeby @thebeebs Tim Berners-Lee's At CERN Web Invented 0 DAYS DECEMBER 20, 1990
4. Martin Beeby @thebeebs 9950 DAYS 19 MARCH 2018
5. Martin Beeby @thebeebs 10,000 DAYS 7 MAY 2018
6. Martin Beeby @thebeebs CAR DAY 10,000
7. Martin Beeby @thebeebs TV DAY 10,000
8. Martin Beeby @thebeebs
9. Martin Beeby @thebeebs ME DAY 10,000
10. Martin Beeby @thebeebs BLOCKCHAIN IS DAY 3335
11. Martin Beeby @thebeebs WHAT IS BLOCKCHAIN WHAT CAN A DEVELOPER DO HOW DO I DO IT
12. Martin Beeby @thebeebs THREE PEOPLE CHRISTER EDWARD DONALD
13. Martin Beeby @thebeebs ALL WORK IN AN OFFICE
14. Martin Beeby @thebeebs CHRISTER THE BAKER
15. Martin Beeby @thebeebs DONALD AND EDWARD BUY DONALD CHRISTER EDWARD
16. Martin Beeby @thebeebs EDWARD BUYS DONALD CHRISTER EDWARD
17. Martin Beeby @thebeebs DONALD BUYS DONALD CHRISTER EDWARD
18. Martin Beeby @thebeebs SOMETMES EDWARD SELLS DONALD CHRISTER EDWARD
19. Martin Beeby @thebeebs CHRISTER BUYS DONALD CHRISTER EDWARD
20. Martin Beeby @thebeebs Handsome Smart Remote Worker NEW PERSON JOINS THE TEAM
21. Martin Beeby @thebeebs MARTIN
22. Martin Beeby @thebeebs Transferring Money between them is now harder Easy to lose track of who owes what Lets build a database MONEY IS A PAIN
23. Martin Beeby @thebeebs Martin Controls it Each cake sale is a transaction The seller tells martin about the transaction. He records it CREATE A DATABASE
24. Martin Beeby @thebeebs TRANSACTIONS DONALD MARTIN CHRISTER EDWARD
25. Martin Beeby @thebeebs Trust Required (Fraud) Transparency Central Control WHAT’S THE PROBLEM?
26. Martin Beeby @thebeebs MOST BUSINESS RUN THIS WAY BIG DATABASES ARE NOT A PROBLEM IF THERE IS TRUST
27. Martin Beeby @thebeebs MARTIN HAS A CAKE PROBLEM
28. Martin Beeby @thebeebs DATABASE FOR EVERYONE DONALD MARTIN CHRISTER EDWARD
29. Martin Beeby @thebeebs Hard to keep in sync Hard to agree Hard to reach consensus PEOPLE COULD STILL DEFRAUD
30. Martin Beeby @thebeebs BLOCKCHAIN
31. Martin Beeby @thebeebs PUBLIC AND PRIVATES DONALD MARTIN Address 1 Address 2 Address 3 Address 6 Address 5 Private Key Private Key Private Key Private Key CHRISTER EDWARD
32. Martin Beeby @thebeebs Sender Amount Receiver Signed Address 1 5 Address 2 110101010 Address 2 4 Address 3 010101010 Address 3 3 Address 1 010011010 TRANSACTIONS
33. Martin Beeby @thebeebs Listen for transactions and validates them Order transactions into a block Creates and hashes blocks solving a maths problem related MINERS LISTEN FOR TRANSACTIONS Sender Receiver Signed Address 1 5 Address 2 110101010 Address 2 4 Address 3 010101010 Address 3 3 Address 1 010011010
34. Martin Beeby @thebeebs Solve a complex problem involving the hashing of the block Would be very expensive to try and present incorrect blocks Miners on bitcoin spend huge sums of money on electric PROOF OF WORK Jargon: A Consensus Algorithm
35. Martin Beeby @thebeebs Proof of Stake Proof of Elapsed Time Byzantine fault tolerant OTHER CONSENSUS ALGORITHM
36. Martin Beeby @thebeebs HASHING In west Philadelphia born and raised on the play ground was where I spent most of my days. Chilling 446F09C5D7DB665A 851077054EBC7067 56E372A32C8753F0 428B6671CA6CE449 In west Trondheim born and raised on the play ground was where I spent most of my days. Chilling 223E8E360399E82A C97B37A73FA1F532 071F03D8A174FA56 6D44F1770CC37D9A SHA256
37. Martin Beeby @thebeebs
38. Martin Beeby @thebeebs Previous Hash of the block All the transactions to create a block Hash the block to create a unique Hash that represents everything YOU CANT CHANGE A BLOCK
39. Martin Beeby @thebeebs OTHER NODES VERIFY
40. Martin Beeby @thebeebs MINERS THEN BUILD ANOTHER
41. Martin Beeby @thebeebs A list of transactions grouped into blocks Blocks chained together by knowing the previous hash Nothing can be altered, the slightest modification would be obvious A BLOCK CHAIN IS Jargon: Merkle Tree
42. Martin Beeby @thebeebs Smart Contracts Private Ledgers Build Apps WHAT CAN A DEVELOPER DO
43. Martin Beeby @thebeebs SMART CONTRACTS
44. Martin Beeby @thebeebs Christer decides to run an incentive. Every 100th cake customer get a reward. Contract Int x AddAddress(address) x = x + 1; If (x =100){ address.transfer(reward) } A PSUEDO CONTRACT
45. Martin Beeby @thebeebs A CONTRACT IS A TRANSACTION
46. Martin Beeby @thebeebs EVERY CALL TO THE CONTRACT REQUIRES A TRANSACTION
47. Martin Beeby @thebeebs MINERS EXECUTE THE PROGRAMS WHILST VERIFYING THE TRANSACTION
48. Martin Beeby @thebeebs The contract code is visible on the blockchain It can’t be changed by anyone All the calls are public and everyone can see the cake competition is fair ITS TRANSPARENT
49. Martin Beeby @thebeebs Bitcoin is great when you have zero trust in the nodes If you have no trust Proof of Work is a good compromise But the electricity cost is the compromise LEVELS OF TRUST
50. Martin Beeby @thebeebs You have trust and want to have decentralised consensus You want to see all the transitions and have distributed consensus You want to add and remove members. ENTERPRISE TRUST ISSUES CAN BE DIFFERENT
51. Martin Beeby @thebeebs https://www.hyperledger.org/members LINUX FOUNDATION
52. Martin Beeby @thebeebs Private and Permissioned Membership Service Provider (MSP) Pluggable: MSP/Consensus/Ledger Format HYPERLEDGER FABRIC Channels
53. Martin Beeby @thebeebs THE TUNA SUPPLY CHAIN From Sea to Table Lots of Fraud Could benefit from Transparency
54. Martin Beeby @thebeebs TUNA SUPPLY CHAIN Sarah is the fisherman who sustainably and legally catches tuna. Regulators verify that the tuna has been legally/sustainably caught. Miriam is a restaurant owner who wants legal/sustainable tuna Carl is another restaurant owner fisherman Sarah can sell tuna to.
55. Martin Beeby @thebeebs Sarah sells at different prices Privacy around deals Carl shouldn’t see Miriams price DEALS NEED TO BE PRIVATE
56. Martin Beeby @thebeebs
57. Martin Beeby @thebeebs package main import ( "fmt" "github.com/hyperledger/fabric/core/chaincode/shim" "github.com/hyperledger/fabric/protos/peer" ) http://thebeebs.co.uk/blockchain CHAINCODE
58. Martin Beeby @thebeebs type Tuna struct { Vessel string ‘json:"vessel"’ Datetime string ‘json:"datetime"’ Location string ‘json:"location"’ Holder string ‘json:"holder"’ } TUNA STRUCT
59. Martin Beeby @thebeebs func (s *SmartContract) initLedger(APIstub shim.ChaincodeStubInterface) sc.Response { tuna := []Tuna{ Tuna{Vessel: "923F", Location: "67.0006, -70.5476", Timestamp: "1504054225", Holder: "Miriam"}, Tuna{Vessel: "M83T", Location: "91.2395, -49.4594", Timestamp: "1504057825", Holder: "Dave"}, Tuna{Vessel: "T012", Location: "58.0148, 59.01391", Timestamp: "1493517025", Holder: "Igor"}, Tuna{Vessel: "P490", Location: "-45.0945, 0.7949", Timestamp: "1496105425", Holder: "Amalea"}, Tuna{Vessel: "S439", Location: "-107.6043, 19.5003", Timestamp: "1493512301", Holder: "Rafa"}, Tuna{Vessel: "J205", Location: "-155.2304, -15.8723", Timestamp: "1494117101", Holder: "Shen"}, Tuna{Vessel: "S22L", Location: "103.8842, 22.1277", Timestamp: "1496104301", Holder: "Leila"}, Tuna{Vessel: "EI89", Location: "-132.3207, -34.0983", Timestamp: "1485066691", Holder: "Yuan"}, Tuna{Vessel: "129R", Location: "153.0054, 12.6429", Timestamp: "1485153091", Holder: "Carlo"}, Tuna{Vessel: "49W4", Location: "51.9435, 8.2735", Timestamp: "1487745091", Holder: "Fatima"}, } i := 0 for i < len(tuna) { fmt.Println("i is ", i) tunaAsBytes, _ := json.Marshal(tuna[i]) APIstub.PutState(strconv.Itoa(i+1), tunaAsBytes) fmt.Println("Added", tuna[i]) i = i + 1 } return shim.Success(nil) } INIT
60. Martin Beeby @thebeebs
61. Martin Beeby @thebeebs func (s *SmartContract) Invoke(APIstub shim.ChaincodeStubInterface) sc.Response { // Retrieve the requested Smart Contract function and arguments function, args := APIstub.GetFunctionAndParameters() // Route to the appropriate handler function to interact with the ledger appropriately if function == "queryTuna" { return s.queryTuna(APIstub, args) } else if function == "initLedger" { return s.initLedger(APIstub) } else if function == "recordTuna" { return s.recordTuna(APIstub, args) } else if function == "queryAllTuna" { return s.queryAllTuna(APIstub) } else if function == "changeTunaHolder" { return s.changeTunaHolder(APIstub, args) } return shim.Error("Invalid Smart Contract function name.") } INVOKE
62. Martin Beeby @thebeebs func (s *SmartContract) queryTuna(APIstub shim.ChaincodeStubInterface, args []string) sc.Response { if len(args) != 1 { return shim.Error("Incorrect number of arguments. Expecting 1") } tunaAsBytes, _ := APIstub.GetState(args[0]) if tunaAsBytes == nil { return shim.Error(“Could not locate tuna”) } return shim.Success(tunaAsBytes) } QUERYTUNA
63. Martin Beeby @thebeebs RECORDTUNA func (s *SmartContract) recordTuna(APIstub shim.ChaincodeStubInterface, args []string) sc.Response { if len(args) != 5 { return shim.Error("Incorrect number of arguments. Expecting 5") } var tuna = Tuna{ Vessel: args[1], Location: args[2], Timestamp: args[3], Holder: args[4]} tunaAsBytes, _ := json.Marshal(tuna) err := APIstub.PutState(args[0], tunaAsBytes) if err != nil { return shim.Error(fmt.Sprintf("Failed to record tuna catch: %s", args[0])) } return shim.Success(nil) }
64. Martin Beeby @thebeebs func (s *SmartContract) changeTunaHolder(APIstub shim.ChaincodeStubInterface, args []string) sc.Response { if len(args) != 2 { return shim.Error("Incorrect number of arguments. Expecting 2") } tunaAsBytes, _ := APIstub.GetState(args[0]) if tunaAsBytes != nil { return shim.Error("Could not locate tuna") } tuna := Tuna{} json.Unmarshal(tunaAsBytes, &tuna) // Normally check that the specified argument is a valid holder of tuna but here we are skipping this check for this example. tuna.Holder = args[1] tunaAsBytes, _ = json.Marshal(tuna) err := APIstub.PutState(args[0], tunaAsBytes) if err != nil { return shim.Error(fmt.Sprintf("Failed to change tuna holder: %s", args[0])) } return shim.Success(nil) } CHANGETUNAHOLDER
65. Martin Beeby @thebeebs
66. Martin Beeby @thebeebs
67. Martin Beeby @thebeebs CALLING SOME CODE // changeTunaHolder - requires 2 argument var request = { chaincodeId:’tuna-app’, fcn: 'changeTunaHolder', args: ['1', 'Alex'], chainId: 'mychannel', txId: tx_id }; return channel.sendTransactionProposal(request);
68. Martin Beeby @thebeebs THEBEEBS.UK/BLOCKCHAIN
69. Martin Beeby @thebeebs WHY ORACLE?
70. Martin Beeby @thebeebs It’s open It’s Flexible I would love your feedback WE HAVE A CLOUD
71. Martin Beeby @thebeebs HTTP://THEBEEBS.UK/TRIAL $300
72. Martin Beeby @thebeebs CONTACT MARTIN BEEBY @thebeebs https://www.thebeebs.co.uk martin.beeby@oracle.com