In this talk, I give an introduction to the concepts behind blockchain and then I get my hands dirty on Ethereum with a hands-on session

1. Introduction to Blockchain
with an Ethereum Hands-on
June 2016
01
by Johann Romefort

2. 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
2

3. 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.

4. 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.

5. What do you need?
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• Terminal
• Code Editor

6. 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)

7. 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.

8. 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

9. 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

10. 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

11. 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”

12. What can I do with a distributed
immutable ledger?
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• Cryptocurrencies
• Property titles
• Notarised acts
• Digital certificates
• And more

13. A gentle introduction to
Ethereum

14. 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.

15. 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

16. 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

17. 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

18. Hands-on!
June 2016
01

19. 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

20. Writing a Smart Contract
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• Language: Solidity (JS-like)
• Supports inheritance
• Compiled with Solc
• Can use tooling to compile and deploy

21. 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

22. 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

23. 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

24. A few words on the DAO
and recent events…

25. Microsoft & Blockchain?
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• Project Bletchey: Blockchain As A Service (BaaS)
• https://azure.microsoft.com/en-us/blog/bletchley-
blockchain/

26. Questions?