Get smarter on Ethereum Smart Contracts with this workshop given by Thomas Vanderstraeten from Cryptizens.io. Feel free to reach out directly to hello@cryptizens.io if you would like to discover more great stuff about Blockchain and Ethereum Smart Contracts!

1. Get smarter on
smart contracts
Thomas Vanderstraeten
https://cryptizens.io
hello@cryptizens.io

2. Starter quiz: where’s the fake blockchain project?
2© Cryptizens.io

3. The plan: go through this together
A sense of how blockchain can run applications
A refresher about blockchain
A point of view on smart contracts biz implications
A ‘get-your-hands-dirty’ exercise
3© Cryptizens.io

4. Blockchain refresher: what lies beyond the buzz?
A DATABASE OF TRANSACTIONS (= LEDGER)
ORGANIZED BY BLOCKS IN A SEQUENTIAL WAY (= CHAIN OF BLOCKS),
SECURED SO IT CANNOT BE COUNTERFEITED (= CRYPTO-MINED),
AND REPLICATED ACROSS MANY COMPUTERS (= DISTRIBUTED)
4© Cryptizens.io

5. A database of transactions
Transactions
DB
Alice sends 3 BTC to Bob
Bob sends 5 BTC to Jeff
Kim sends 1 BTC to Alice
5© Cryptizens.io

6. Organized by blocks in a sequential way
Block N - 2
before
Jeff sends 1 BTC to Alice
Bob sends 1 BTC to Kim
Alice sends 1 BTC to Bob
Block N - 1
yesterdayDB
Alice sends 3 BTC to Bob
Bob sends 5 BTC to Jeff
Kim sends 1 BTC to Alice
Block N
today
6© Cryptizens.io

7. Secured so it cannot be counterfeited
Block N - 2
before
Block N - 1
yesterday
Block N
today
Transactions
Alice sends 3 BTC to Bob
Bob sends 5 BTC to Jeff
Kim sends 1 BTC to Alice
Transactions
Alice sends 3 BTC to Bob
Bob sends 6 BTC to Jeff
Kim sends 1 BTC to Alice
7© Cryptizens.io

8. Replicated across many computers
Alice’s
computer
DB
Jeff’s
computer
DB
Charles’s
computer
DB
Bob’s
computer
DB
Kim’s
computer
DB
8© Cryptizens.io

9. Blockchain’s resulting properties in a nutshell
Transparency
& auditability
Immutability
Decentralization
Common single
source of truth
Desintermediation
9© Cryptizens.io

10. In 2013, this guy created a blockchain to run apps
I’ve got a nice t-shirt, but what
about something nicer yet?
Let’s leverage blockchain’s
properties to run applications
called smart contracts!
Vitalik Buterin, Ethereum blockchain creator
10© Cryptizens.io

11. What is an app, fundamentally?
Data
base
Server
that runs
code
End-user
interface
Simple Web application architecture
11© Cryptizens.io

12. So, how can we use the blockchain to run apps?
Transactions
Alice sends 1 ETH
to CryptoKitties.co
DB
Start from a simple
‘financial transactions’
blockchain...
State of the world
Kitty_owner = Alice
Kitty_hungry = true
Transactions
Alice sends 1 ETH
to CryptoKitties.co
DB
...add general purpose
storage to play with
variables...
State of the world
Kitty_owner = Alice
Kitty_hungry = true
Transactions
- Alice sends 1 ETH to
CryptoKitties.co
- Alice feeds the cat
Functions
feedCat(cost = 0.5 ETH)
buyCat(cost = 1 ETH)
VM
DBSmart contract
...add functions to modify
these variables, and a
virtual machine to run these
functions...
© Cryptizens.io
Smart contract
State of the world
Kitty_owner = Alice
Kitty_hungry = true
Transactions
- Alice sends 1 ETH to
CryptoKitties.co
- Alice feeds the cat
Functions
feedCat(cost = 0.5 ETH)
buyCat(cost = 1 ETH)
VM
DB
Website interface
feed buy
WebBlockchain
...add a sexy web front-end to
trigger these functions, and
you’re done!
Decentralized App (Dapp)
UI
12

13. Blockchain properties can thus be leveraged for apps!
Transparency
& auditability
Immutability
Decentralization
Common single
source of truth
Desintermediation
Everyone sees the
application code,
so no malicious
features can be
hidden
No one can alter the
the code after it has
been deployed
All participate in
the running of the
application
No single
stakeholder owns
the app for their
single benefit
All can agree on
a common set of
functions and
data
SMART
CONTRACT
13© Cryptizens.io
TECHNICAL POINT OF VIEW

14. And that’s how the term ‘smart contract’ was coined
SMART
CONTRACT
It not only
documents the
agreement, but
also enforces it
(code execution)
Cannot be
changed once it
has been signed
(deployed on the
blockchain)
Documents an
agreement
(implements a series
of functions with
triggers and effects)
Is public and
auditable for all
stakeholders
(distributed on the
blockchain)
Basically, just a computer
program (running on the
Ethereum virtual machine)
14© Cryptizens.io
BUSINESS POINT OF VIEW

15. Smart contracts applied to business: a lottery
Organizer
Participants
WITHOUT SMART CONTRACT
Payment provider
Escrow account
Lottery
Terms &
conditions
Company
statuses
Payments
Terms &
conditions
Winner pick
15© Cryptizens.io
We’ve built a complex ecosystem
of stakeholders, laws, processes
and documents to embed TRUST
in interactions, and protect people
in case of breaches!

16. Smart contracts applied to business: a lottery
Participants 16© Cryptizens.io
SMART
CONTRACT
Organizer
Who cares about trust? Smart
contracts technology allows us to
interact in a TRUSTLESS way,
where technology prevents
breaches of agreements! Meow!
WITH SMART CONTRACT

17. A real-life insurance smart contract: AXA Fizzy
17© Cryptizens.io
Oops...

18. My nonprofit smart contract venture: Cryptorun
60 KM around Brussels
SMART
CONTRACT
if ThomasHasRun60Km {
sendFundsToBeCode();
}
18© Cryptizens.io

19. A critical look at smart contracts business use
Still hard to connect to the outside world
without losing trust
Smart contract engineers might become the
lawyers of tomorrow
Immutability goes against lean development
Infancy issues (scalability, reliability)
? But yet, so much potential!
19© Cryptizens.io

20. Now, let’s get our hands dirty!
https://etherlearn.io
20© Cryptizens.io

21. First thing first: get some free (test) Ether!
21© Cryptizens.io
Install Metamask
wallet
Note your Rinkeby
account address
Post your address
on Google+
Paste the G+ post
link in the faucet
metamask.io plus.google.com faucet.rinkeby.io
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=> then, restart
your browser!

22. And now, let’s deploy!
22© Cryptizens.io
Go on Etherlearn Click on deploy Check Etherscan Interact with it
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etherlearn.io etherlearn.io rinkeby.etherscan.io etherlearn.io