Code on the chain! An introduction in writing smart contracts and tooling for Blockchain Development - Tom Davies/Vallard Benincosa - Codemotion Amsterdam 2018
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We've all heard of bitcoin and also blockchain, the technology that underpins it. But how do you develop on blockchain? How do you create your own smart contracts? In this session, you'll get to understand the basics of blockchain development. We’ll provide a brief blockchain overview, describing the concepts and mechanisms of the technology, before we take you through creating your very own crypto token, introducing some basic developer tool chains and walking through your first smart contracts using Ethereum, the popular public blockchain.
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Code on the chain! An introduction in writing smart contracts and tooling for Blockchain Development - Tom Davies/Vallard Benincosa - Codemotion Amsterdam 2018
- 1. Tom Davies, Sr. Manager, Cisco DevNet, Vallard Benincosa, Software Engineer, Cisco Code on the Chain! An introduction to writing smart contracts & tooling for blockchain development
- 2. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Extended Leadership Planning Review 4/24/2018 <me> @TomDavies_UK </him> @vallard
- 3. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Developer Advocacy “Voice of Developer” DevNet Community, Customer Engagements, DevNet Express, Partners, WWSE Learn CodeInspire Connect
- 4. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential DevNet Data as of April 10, 2018 DevNet Community 72,500+ Learning Labs completed 490,000+ Members 33,000+ Companies 60,000 Avg. Monthly Active Users
- 5. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Learning Labs Sandbox Events Portal & Microsites Support Code ExchangeCo-Creations Join us @ developer.cisco.com
- 6. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential • Blockchain Fundamentals • Your First Contract: • Developer Tooling & Toolchains • Contracts & Deployments • Observability • You’re up! Buy some DevNetCoin! Agenda
- 7. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Blockchain Fundamentals
- 8. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Everyone has a full copy | No one entity controls it or the transactions | Cryptographically secure - ‘trustless’ Transactions –> Blocks -> Chain What is a blockchain? A transactional database!
- 9. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Alice Bitcoin Balance: 3 BTC ~ $30,000 1AHw1E7L2tNxj29wtEATPEMc1Mj77F22Yt Coffee Shop Bitcoin Address: 1KfDuF4g5k8oTbvamp9BYzPLKrYbnpyT3m Alice has a public and private key A transaction to send 0.00025 bitcoins is signed with Alice’s private key and the coffee shop’s public key Coffee shop advertises public key
- 10. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Alice Bitcoin Address: 1AHw1E7L2tNxj29wtEATPEMc1Mj77F22Yt Coffee Shop Bitcoin Address: 1KfDuF4g5k8oTbvamp9BYzPLKrYbnpyT3m 0.00051 BTC
- 11. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential 1AHw1E7L2tNxj29wtEATPEMc1Mj77F22Yt TPEMc1Mj77F22YtwtEA HudeW7OoXane3zeeaeyoh3Laayei6Bi ephahS9GeJohyej1oyeec1He5seam3Quitub1EizoMo7eebieiePohcu7mei0ohGhahsee9EePohb1bohcoa2bi2GIez ei3sozaiThoo9tod4dahSIazahf3ixei3MaibRoutei9uchahT0juIoch2GahPetie0ahgahiex2VAiph7yohca0Ain6 uquoosh2UUu5Xah0oOhp0ahNaDie8li2vXo2taiquiekeeMa2ohK3eewicoGhe9ieooy5vo7JUyei9airAo8mufohIeg aib3aeefe4ieXdiuF7EiLUijeiPe9eegh4ohPIog1daihAhf1lu0zgieD2zoowobaeTh4ieH9iecaiuch4Eedeavei3e NSeihae3vShaefae9ai9uzooNIej7ohyeque9TaifseeFie3nau2EiroueeV0kiChahc7Dahszu4fee0AeiXee0TuAWa iv5siiqu0Queieasee4XooowoSh6OohngaeH5eexahZ7ijoo3io3Hquaiqu4EfiWoo7neaseuCh1AARoh0weelavaes3 ExeePei9nEeyahp7Jve4yeBaeEeCaF2aeaXiF9feunooN0oshvaK1Cahnthohg1BoaiF4ahG6EiXi6CeinahX6oofxe6 Ti0ovxah5QuaeUo5Thei6Bea8ahshaiQuiG6Areiw5jiYPhahxoo7aiGh0chiDie0iQuaIuk1eiphKiiphe4eeeCa3ka ereh2Jai6Xuvai1huohz6EeciahDe8oa7shohCor6Pon1roo7Ietho6AeChoa8ou6Chais6ieCe0VuoyeEer6nie3Noo 7seePGeuph2ivAis4xeivjooM5wooteeN3xooov4thaeJOodah3uuob4In1oceiL9QuebohM7Jah1deJoo1WoDun3se8 oKae7eeXahaDu9eiLzuoFi8ohiew8EsopohN3ahquphe1Xaetsu9AthieoubeeS8UAwu0zeejAhvie1lovahNgai8xae 7FieGthu4aTh7Phahkae9sifu9Niprae1Coofmohh1eeSzuNgoh3yEeGh1aj4Choh2iLuEighae2aEij3kohhEezou6E ieisee3WooD8iuH3xphe9PaecUp4duvieNeera0kout1EipiaJoh3iet7ohd9Bophgoop5EewEechah6lWohpoh5aooT Blocks are simply a ledger of transactions 0.00025 BTC A block is a list of transactions that are collected by the peer 2 peer network Alice’s Account Coffee Shop Account
- 12. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential How do you stop abuse & double spend? • Race to create the next block in a blockchain • New bitcoin block is created every 10 minutes Miners!
- 13. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Proof of Work • A Hash is a one way function • Nearly impossible to guess • Easy to verify • Header Hash must be less than a specified target value (e.g.: begins with x amount of 0’s.) • Nonce is only part that can change to get value. • Must iterate to find value 1AHw1E7L2tNxj29wtEATPEMc1Mj77F22Yt TPEMc1Mj77F22YtwtEA HudeW7OoXane3zeeaeyoh3Laayei6Bi ephahS9GeJohyej1oyeec1He5seam3Quitub1EizoMo7eebieiePohcu7mei0ohGhahsee9EePohb1bohcoa2b i2GIezei3sozaiThoo9tod4dahSIazahf3ixei3MaibRoutei9uchahT0juIoch2GahPetie0ahgahiex2VAip h7yohca0Ain6uquoosh2UUu5Xah0oOhp0ahNaDie8li2vXo2taiquiekeeMa2ohK3eewicoGhe9ieooy5vo7JU yei9airAo8mufohIegaib3aeefe4ieXdiuF7EiLUijeiPe9eegh4ohPIog1daihAhf1lu0zgieD2zoowobaeTh 4ieH9iecaiuch4Eedeavei3eNSeihae3vShaefae9ai9uzooNIej7ohyeque9TaifseeFie3nau2EiroueeV0k iChahc7Dahszu4fee0AeiXee0TuAWaiv5siiqu0Queieasee4XooowoSh6OohngaeH5eexahZ7ijoo3io3Hqua iqu4EfiWoo7neaseuCh1AARoh0weelavaes3ExeePei9nEeyahp7Jve4yeBaeEeCaF2aeaXiF9feunooN0oshv aK1Cahnthohg1BoaiF4ahG6EiXi6CeinahX6oofxe6Ti0ovxah5QuaeUo5Thei6Bea8ahshaiQuiG6Areiw5ji YPhahxoo7aiGh0chiDie0iQuaIuk1eiphKiiphe4eeeCa3kaereh2Jai6Xuvai1huohz6EeciahDe8oa7shohC or6Pon1roo7Ietho6AeChoa8ou6Chais6ieCe0VuoyeEer6nie3Noo7seePGeuph2ivAis4xeivjooM5wootee N3xooov4thaeJOodah3uuob4In1oceiL9QuebohM7Jah1deJoo1WoDun3se8oKae7eeXahaDu9eiLzuoFi8ohi ew8EsopohN3ahquphe1Xaetsu9AthieoubeeS8UAwu0zeejAhvie1lovahNgai8xae7FieGthu4aTh7Phahkae 9sifu9Niprae1Coofmohh1eeSzuNgoh3yEeGh1aj4Choh2iLuEighae2aEij3kohhEezou6Eieisee3WooD8iu H3xphe9PaecUp4duvieNeera0kout1EipiaJoh3iet7ohd9Bophgoop5EewEechah6lWohpoh5aooT Block Header ( 80 bytes ) Block Body • 32 bytes of previous block hash • 32 bytes of Merkle root hash • Timestamp • Nonce
- 14. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Block is broadcast to Bitcoin P2P network
- 15. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Block…chain Blockchain means that each block header refers back to the previous block. • Consensus comes by the longest block chain • Only one winner – encourages hashing pools • Works as long as 51% of network arrives to consensus • Encourages compute resources to be honest • In Bitcoin only 21 million coins will ever be created. 75% of all coins that will ever be created have already been mined. Last coin estimated in 2140.
- 16. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential • Bitcoin allows scripting but not Turing complete • Ethereum adds ability to run code in blockchain • Smart contracts create a state machine • Growing ecosystem of tools and projects Ethereum There’s more than just the bitcoin blockchain!
- 17. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential How do blockchains work? • Smart Contracts Triggers Smart Contracts
- 18. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential • Stored Procedures • Can cause massive problems! DOA lost 3.6 million ether! • Tooling is rapidly developing • Many platforms to run on • How expensive is it to run on Ethereum? • Anyone can make their own currency! Smart Contracts
- 19. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Distributed Applications (DApps) Architecture Application UI Smart Contracts (Application Logic) Database (Decentralised Compute / Storage)
- 20. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential A Note On Blockchain Types Public Private Community PermissionedNon-Permissioned
- 21. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Creating Your First Contract Standards, Tools, Toolchains
- 22. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Let’s create our own token The DevNet ICO! (Initial Coin Offering)
- 23. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Let’s create our own token ICO Details Tom Val 20 Million 5 Million 5 Million You Guys 10 Million 1 ETH = 100 DevCoin Does this sound like a good ICO? YES…if you’re Tom or Val. ERC20 Standard – Our Symbol: DEV * https://theethereum.wiki/w/index.php/ERC20_Token_Standard*
- 24. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Tools to use to become millionaires Ethereum Ecosystem Deploying Contracts / Buying & Sending Ether IDEs for writing our Smart Contracts Blockchains for testing and finally releasing our contracts Writing Deploying Platform Contracts
- 25. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Toolchains: IDE, Deployment Tool, Test Network Solidity IDE Test Network (Ethereum Based) contract Contract Deployment Inspect Funds / Deployment Contract ID UI Based Test Network (Ethereum Based) contract Contract Deployment Inspect Funds / Deployment Contract ID Text Editor Command Line ATOM
- 26. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Smart Contract Language - Solidity http://solidity.readthedocs.io/en/develop/contracts.html The Ethereum Contract Programming Language • Used to write Smart Contracts – Contract Orientated • Used on other blockchains as well as Ethereum Fun Fact: Contracts can create new contracts!
- 27. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Show me a Solidity ContractERC20 Compliant, baby!
- 28. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Toolchain: IDE, Deployment Tool, Test Network Text Editor Test Network (Ethereum Based) contract Contract Deployment Inspect Funds / Deployment Contract IDATOM
- 29. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Why use a blockchain test network? Ether, used to pay for executing code, is expensive: $392 -> 1ETH Instead: – Chose a test network to experiment • Kovan: https://github.com/kovan-testnet/proposal • Rinkeby: https://gist.github.com/cryptogoth/10a98e8078cfd69f7ca892ddbdcf26bc – Create Account / Address • Use https://www.MyEtherWallet.com or Metamask Browser plugin • Select correct network – Visit Faucet addresses to get Ether in your account • Kovan: https://gitter.im/kovan-testnet/faucet • Rinkeby: https://faucet.rinkeby.io/ – Get funded with test ether!
- 30. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Go on…Deploy the DevNetCoin Contract!
- 31. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Toolchain: IDE, Deployment Tool, Test Network Text Editor Test Network (Ethereum Based) contract Contract Deployment Inspect Funds / Deployment Contract IDATOM
- 32. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Contract Observability
- 33. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Let me see inside the blockchain!
- 34. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Toolchain: IDE, Deployment Tool, Test Network Text Editor Test Network (Ethereum Based) contract Contract Deployment Inspect Funds / Deployment Contract IDATOM DevNet Coin is Live! Buy here: www.DevNetCoin.com
- 35. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential I want some DevNetCoin! Show me how to get some!
- 36. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Get DevNetCoin - Example • Create account with Metamask / MyEtherWallet on KOVAN network • Copy address into https://gitter.im/kovan-testnet/faucet (Don’t be greedy)
- 37. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Buy DevNetCoin! DevNetCoin Contract Address ------->
- 38. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential Continue Your Learning…
- 39. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential DevNetCoin www.DevNetCoin.com
- 40. © 2017 Cisco and/or its affiliates. All rights reserved. Cisco Confidential DevNet Sandbox developer.cisco.com/sandbox
Editor's Notes
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- Val In this peer 2 peer network an actor on the network can be what is called a miner. A miner is a participant who tries to create the next block in the blockchain. The miners are incentivized in two ways: As part of creating a block they create new tokens that they own They get commissions or a percentage of the transactions Mining on some networks can be done with commodity hardware. Monero for example I’ve managed to run on a few UCS servers. But the more famous blockchains require special hardware due to competition. One example is Bitcoin which requires special ASICs. Even GPUs aren’t good enough for Bitcoin anymore and ASICs such as the Antminer S9 have been popular. You can buy some of these on eBay or other aftermarket sites. I have an S9 that I bought with Bitcoin cash that runs and at one point was making 20 euro a day.
- Val Essentially each miner is trying to come up with the next block, but its not as easy as just putting together a bunch of transactions. They need to also do what is called ”Proof of Work”. Some blockchains have other consensus protocols such as ”Proof of Stake” but the original Bitcoin and many others are derived from “Proof of work”. Essentially, we’re trying to take all the transactions, hash them together and then come up with a hash that starts with a certain amount of zeros. This idea of a hash is a “One way function”. From algebra, you are familiar with simple functions like y = x^2. If I give you x = 2, you know y = 4. If you’re advanced enough in your algebra, if I give you a number like 144 and say that is y, you can tell me that x was 12 or -12. This is a two way function, we can simply find x if we know the value of y and the function. A one-way function is more complex in that if I give you y it is nearly impossible for you to tell me what x was. The only way you can do it is by brute force. In bitcoin we use the eliptical curve function which would take a computer thousands of years to figure out x given y. The beauty, however of a one-way function is that if I give you y and then give you x, then you can verify that x does indeed give you y in a super fast O(1) computation. In blockchain, we take a hash of the transactions, the timestamp, and the previous block and something called a nonce and run it through this one-way function each time trying to come up with some number that begins with a certain amount of zeros. The only thing we can change is the nonce, and we just brute force it until something comes up. Because this is an all or nothing game, many miners “pool” there servers together so that if one lucky miner finds the magic nonce, the miners all share the reward based on their percentage of hashing power contributed towards the search.
- Val Once the right nonce is found, the block is broadcast to the network. The other servers can validate the correctness of the block. If it checks out that block becomes the next block on the chain. Several miners may come up with a different block they think should be the next block and that is actually valid. The network holds on to both of those blocks. Then as subsequent miners mine blocks they base it on one of the previous blocks. The block with the longest history becomes the “real block” and eventual consensus is made.
- Val This eventual consensus is one of the beauties of the chain. In the original paper by Satoshi Nakamoto, the word “block chain” is not even mentioned. The word comes from the fact that each header of a new block must refer back to a previous block. This enjoys the property that altering even one transaction way back in the chain would change the entire chain and so the chain is tamper and censor resistent. In bitcoin this works and encourages would be hackers to instead contribute resources towards keeping the block fare. In bitcoin only 21 million coins will be created. After that point in 2140 miners will be incentivized only by collecting fees for including transactions in their blocks.
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