Fintech Meetup 20160705 - Smart Contracts

http://www.meetup.com/FinTech-Ireland/events/231968414/
We will present an overview of a number of different APIs from payment, banking, cryptocurrency, blockchain and smart contracts. The session should be about and hour and each API limited to 15/20 minutes. Networking and discussion afterwards.

• Smart Contract - a demo and walkthrough from Vineet Singh of Citi.

Vineet is an innovation lead in Citi Innovation Lab Dublin. He leads Citi’s work in blockchain and smart contract research. Supply Chains and Trade finance are the business areas when vineet hopes to make block chain’s a reality. He is a huge proponent of public chains and also represents Citi TTS in R3 group of Consortium. Vineet has a Master’s in in distributed systems and peer to peer networks from Trinity College Dublin.

Transcript

1. Smart Contracts @ Ethereum By Vineet Kumar Singh Innovation Lead, Citi Innovation Lab HyperLedger Corda
2. Smart Contracts @ Ethereum By Vineet Kumar Singh Innovation Lead, Citi Innovation Lab HyperLedger Corda
3. Contracts don't make anything possible that was previously impossible, but rather, they allow you to solve common problems in a way that minimizes trust. Minimal trust often makes things more convenient by allowing human judgements to be taken out of the loop, thus allowing complete automation*. *https://en.bitcoin.it/wiki/Contract
4. Decentralized provable execution of logic. A smart contract’s state is stored on the public blockchain. A smart contract program is executed by a network of miners who reach consensus on the outcome of the execution, and update the contract’s state on the blockchain accordingly. Users can send money or data to a contract; or receive money or data from a contract
5. Block i Block i+1 Block i+2 Block i+3 Block i+4 Mined Block Code Storage Miners Contracts Users Turing Compatible Smart Contracts Compatible Blockchains Data Money Blockchain
6. Contract Development Solidity, Serpent, LLL Contract Interaction WEB3 Javascript Module
7. Contract Development Key Concepts
8. Solidity Contracts • State Variables • Functions • Function Modifiers • Events • Structs • Enum Types Contracts in Solidity are similar to Classes in Object Oriented Languages.
9. State Variables contract SimpleStorage { uint storedData; // State variable // ... } • external • public • internal • private
10. Functions contract SimpleAuction { function bid() { // Function // ... } }
11. Function Modifiers contract Purchase { address public seller; modifier onlySeller() { // Modifier if (msg.sender != seller) throw; _ } function abort() onlySeller { // Modifier usage // ... } }
12. Events contract SimpleAuction { event HighestBidIncreased(address bidder, uint amount); // Event function bid() { // ... HighestBidIncreased(msg.sender, msg.value); // Triggering event } }
13. Structs contract Ballot { struct Voter { // Struct uint weight; bool voted; address delegate; uint vote; } }
14. Enums contract Purchase { enum State { Created, Locked, Inactive } // Enum }
15. Walkthrough: Escrow Contract Selling goods over the internet without any trusted third party
16. Bob Alice 1. Buyer is scammer ??
17. Bob Alice Buyer is scammer ??
18. Alice Buyer is scammer ?? ??
19. Bob Alice 2. Seller is scammer ??
20. Bob Alice 2. Seller is scammer ??
21. Bob 2. Seller is scammer ?? ??
22. Bob Alice Use an Escrow third Party Eve
23. Bob Alice Use an Escrow Third Party Eve
24. Bob Alice Use an Escrow Third Party ?? ??
25. Bob Alice Two Party Escrow original idea Oleg Andreev
26. Bob Alice Two Party Escrow Seller puts 2x amount
27. Bob Alice Two Party Escrow Buyer puts amount + deposit
28. Bob Alice Two Party Escrow Buyer puts amount + deposit
29. Bob Alice Two Party Escrow Buyer Confirms: Received Buyer gets deposit, Seller gets deposit + sale
30. Bob Alice Two Party Escrow Buyer unhappy with goods Received Seller refunds or money in escrow until they resolve
31. Code
34. Web3 API’s
35. Directory Structure
36. Checking for the RPC Connection to Local Node
37. Compiling the Solidity Contract
38. Deploying Contract To Blockchain
39. Secure Contract Principles... • Error in encoding state machine. • Failing to use cryptography. • Misaligned Incentives. Ethereum Specific Mistakes • Call stack bug • Blockhash bug • Not checking return value of sender.send();
40. Thank You