Introduction to Blockchain with an Ethereum Hands-on

June 2016

01by Johann Romefort

About Johann• Tech Evangelist @Stylight

• 15+ years in tech

• In Germany for 2 years

• 7 years in San Francisco doing startups

• Organizer of many meetups

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Agenda - Introduction

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• What is blockchain, what is Ethereum, and what about Bitcoin?

• Basic concepts of Ethereum:

• Ether

• Wallet

• Transactions, Blocks, Smart Contracts, ĐApps and The Ethereum Virtual Machine.

Agenda - Hands-on

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• Local, Test and Production blockchains. Let's browse them, and find transactions.

• How to get the first Ether in your wallet.

• Get a local Ethereum node running and make your first transaction.

• Write, compile and deploy a Smart Contract with Truffle.

• Invoke your Smart Contract and see your transactions.

• - Where is this going? A quick intro to the DAO and potential future use cases of the technology.

What do you need?

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• Terminal

• Code Editor

What is blockchain?

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• Blockchain is the technology behind bitcoin .

• Bitcoin was created in 2008 by Satoshi Nakamoto

• Ethereum is a blockchain 2.0 - it retains the same principles but add some new ones (like Smart Contracts)

Blockchain principles

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The Blockchain is a distributed public ledger. An ordered and timestamped record of transactions. This system is used to protect against double spending and modification of previous transaction records.

What is a “Hash”?

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A hash function is a type of mathematical function which turns data into a fingerprint of that data called a hash:

SHA-256 of “Hello from Microsoft”:

a11a19a7a180e0d0f5173fd89a77ff67fde082f59f75d157ca1aa3395411e30b

SHA-256 of “Hello from Microsoft!”:

d9b8515817907bdebfa29d4b7591f7336035ecf3bed3bedda93e2a9a10a0f896

Properties of good Hashing functions

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• Impossible to deduce the data from the hash

• Slight change to data modify the hash in a very unpredictable way

What is a “Block”?

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• Bundles transactions

• Containers previous block hash

• Blocks are linked through their hashes

• You can’t change the data in one block in the chain without changing the subsequent chain

• Unless you mine it all over again

A few words about Mining

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• Mining is computationally expensive (on purpose)

• Mining a block means guessing a hash that matches particular criteria

• Miners can’t change the transaction data, but only something called a “nonce”

• finding the right nonce that makes the hash of the block match a particular criteria is called the “proof of work”

What can I do with a distributed immutable ledger?

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• Cryptocurrencies

• Property titles

• Notarised acts

• Digital certificates

• And more

A gentle introduction to Ethereum

What’s Ethereum?

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• Initially conceptualised in 2013 by Vitalik Buterin

• Development was crowdfunded and launched in July 2015

• “A Next-Generation Cryptocurrency and Decentralized Application Platform”

• Does not rely on the bitcoin blockchain

• Ether (ETH) is the “fuel” to operate the platform.

What’s the Ethereum Wallet?

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• Entry point in the Ethereum platform

• Holds your accounts

• Let you send/receive ETH

• Let you create / invoke Smart Contracts

What’s a Transaction?

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• In Ethereum’s world it’s an operation that writes data on the blockchain

• You have to pay a fee for each transactions you make

• the simplest transaction is sending ETH from one account to another

• More complicated transaction involve Smart Contracts

What’s a Smart Contract?

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• It’s code running on the Ethereum Virtual Machine

• A Smart Contract can hold Ether, write data to the blockchain and be invoked from another Smart Contract.

• It’s written using one of the supported language, most likely Solidity

Hands-on!

June 2016

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Browsing the blockchain

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• A few web interface available

• Ether.camp is great : https://live.ether.camp/

• Different chains for different purposes:

• Homestead: “production”

• Morden: Staging

• Local testrpc : https://github.com/ethereumjs/testrpc

Writing a Smart Contract

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• Language: Solidity (JS-like)

• Supports inheritance

• Compiled with Solc

• Can use tooling to compile and deploy

Installing Geth

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• https://github.com/ethereum/go-ethereum/releases

• Launching Geth:

$ geth --rpc \ --rpcaddr 0.0.0.0 --rpccorsdomain "*" --rpcapi "eth,web3" \ --unlock 0 \ console

Truffle - A development framework for Ethereum

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• https://github.com/ConsenSys/truffle

• Built-in contract compilation, linking, deployment

• Interactive console for managing deployed contracts

Play around with Truffle

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• List of commands

• Initialise a project

• Compile a contract

• Deploy a contract

• Make a call

• Make a transaction

• Build a front-end

A few words on the DAO and recent events…

Microsoft & Blockchain?

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• Project Bletchey: Blockchain As A Service (BaaS)

• https://azure.microsoft.com/en-us/blog/bletchley-blockchain/

Questions?