Why you should be interested in the blockchain

#chainskills #devoxx

Why you should really care about the blockchain?

Sébastien Arbogast - Said Eloudrhiri

@sarbogast @eloudsa

Who are we?

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@sarbogast @eloudsa


Sébastien Arbogast

#chainskills

• Software developer for 11+ years

• Agile practitioner

• Lean Startup coach

• Entrepreneur

• Mobile and Apple TV developer

• futurologist.co

• Blockchain enthusiast3

@sarbogast @eloudsa


http://futurologist.co

Said Eloudrhiri

#chainskills

• Developer since 1992

• Agile Coach, ScrumMaster, Team Lead

• Devoxx4Kids trainer, Wajug organizer

• Android developer (Pixync, Smartvoxx, My Devoxx, TVoxx)

• Blockchain developer (ChainSkills)

• Fatherologist (Nora, Rayane and Djenna)

• Founder of Noratek4

@sarbogast @eloudsa


We are developers, not traders

#chainskills 5

@sarbogast @eloudsa


We are enthusiasts, not experts

#chainskills 6

@sarbogast @eloudsa


What is the blockchain?

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@sarbogast @eloudsa


@sarbogast @eloudsa


2008

Satoshi Nakamoto

Whitepaper

Code base

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Concepts

Implementations

Instances

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Concepts

Implementations

Instances

Transaction order and state

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@sarbogast @eloudsa


Account holder Balance

Alice 15

Bob 5

John 10

From To Amount

Alice Bob 5

Bob John 10

John Alice 5


Alice 10

Bob 10

John 10


Alice 10

Bob 0

John 20


Alice 15

Bob 0

John 15

Scenario #1


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@sarbogast @eloudsa



Alice 15

Bob 5

John 10

From To Amount

Bob John 10

John Alice 5

Alice Bob 5


Alice 20

Bob 5

John 5


Alice 15

Bob 10

John 5

Scenario #2


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• State depends on order of transactions

• When you have one database and only one way to access it, it's easy

• But: • What happens if someone changes the order or the state directly? (mutability) • What if the database fails? (fault tolerance) • Who can see what? (censorship)

@sarbogast @eloudsa


In a centralized system

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• Mutability: complex authorization and audit logging

• Fault tolerance: redundance, but then cross-server transactions so expensive middleware

• Censorship: APIs with complex security

@sarbogast @eloudsa


In a distributed and decentralized database

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• Data is distributed on all the nodes in the system

• Control over that data is decentralized too

• Fault tolerance: peer-to-peer distributed network

• Transparency: every node has all the data

• Anonymity: to protect data privacy despite distribution

• Immutability: consensus algorithm

@sarbogast @eloudsa


How do you reach consensus?

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• Transactions are ordered and bundled in blocks

• Blocks are chained together

• A consensus algorithm determines the order of blocks in a distributed mode

• Every node can verify that this order is cryptographically valid

@sarbogast @eloudsa


@sarbogast @eloudsa


Concepts

Implementations

Instances

Bitcoin Ethereum Ethereum Casper

Consensus algorithm Proof-of-Work Proof-of-Work Proof-of-Stake

Mining rewardStatic mining reward

(12,5BTC) halved every 4 years + transaction fees

Static mining reward (5ETH) + uncles + transactions fees +

gas

Bet rewards + transaction fees + gas

Block time ~10 minutes ~10 seconds ~4 seconds

Various implementations of these concepts

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@sarbogast @eloudsa


Con

cept

sIm

plem

enta

tions

Inst

ance

s

@sarbogast @eloudsa


Concepts

Implementations

Instances

Different instances of the same implementation

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• Blockchain = code base for node software (with consensus algorithm)

• Blockchain instance = • Genesis block • Network identifier • Chain of blocks built by software

• So if you change the software on some nodes, you build a forking chain

@sarbogast @eloudsa


Con

cept

sIm

plem

enta

tions

Inst

ance

s

Why do you need a crypto-currency?

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• To incentivize the nodes to participate in consensus algorithm (game theory)

• To discourage splits and build trust

• As a backing asset to transfer value

• On Ethereum, to pay for the execution of smart contracts

@sarbogast @eloudsa


It started off as a currency

#chainskills 22

@sarbogast @eloudsa


Source: www.kraken.com

http://www.kraken.com

You can pay for stuff in crypto-currencies

#chainskills 23

@sarbogast @eloudsa


@sarbogast @eloudsa


What is it useful for?

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@sarbogast @eloudsa


A payment transaction

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@sarbogast @eloudsa


If balance(A) > X, then decrease(A,X) and

increase (B,X)

State S1 State S2

Account A Account B Account A Account B

A payment blockchain

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@sarbogast @eloudsa


A generic transaction

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@sarbogast @eloudsa


Any modification on any number of variables of any account

State S1 State S2

Account A Account B Account A Account B

A generic blockchain

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@sarbogast @eloudsa


Everywhere there is a registry of ordered transactions nobody should be able to tamper with

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@sarbogast @eloudsa


Each transaction involves business logic

#chainskills 31

@sarbogast @eloudsa


In a blockchain, business processes are coded into smart contracts

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@sarbogast @eloudsa


A distributed application (Dapp) is a set of smart contracts with a user interface

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UI

0x123 0x456 0x789

A few Dapps

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What is a DAO?

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@sarbogast @eloudsa


Token holdersContractorsBenefits

Value increase

Split

ALPHA

What is it NOT useful for?

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@sarbogast @eloudsa


Blockchain = design pattern

#chainskills 37

@sarbogast @eloudsa



First rule of the blockchainYou don't need a blockchain!

@sarbogast @eloudsa

Transparency and anonymity

#chainskills 39

@sarbogast @eloudsa


www.blockchain.info

www.etherscan.io

http://www.blockchain.info

http://www.etherscan.io

Pay-to-participate

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@sarbogast @eloudsa


Value at time of transaction0.16 USD

Distributed consensus is slower

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@sarbogast @eloudsa


VISA (2000) Paypal (115) Bitcoin (7) Ethereum (20)

Transaction confirmation times are long

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@sarbogast @eloudsa


Bitcoin (6 blocks x 600s) Ethereum (12 blocks x 17s) REST (~500ms)

System evolution is slow

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@sarbogast @eloudsa


Soft forks are forward compatible Hard forks are NOT forward compatible

Requires miners to switch Requires everyone to switchRestricts block acceptance rules Eases block acceptance rules

Data storage is very limited

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• Store data elsewhere, store the hash in the chain

• But then your file storage needs to be distributed too

• The bigger your chain, the more restricted it gets in terms of devices

@sarbogast @eloudsa


June 2016 Bitcoin Ethereum

Blockchain size ~71GB ~22GB

Growth/month ~4GB ~2GB

You need a decision model

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@sarbogast @eloudsa

#chainskills #devoxxhttps://medium.com/@sbmeunier/when-do-you-need-blockchain-decision-models-a5c40e7c9ba1#.vwz9bni3b

How do you develop on it?

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@sarbogast @eloudsa


The communities

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• Forums on Reddit: /r/ethereum and /r/bitcoin

• News: steemit.com, CoinDesk, BitcoinMagazine

• Questions: bitcoin.stackexchange.com, ethereum.stackexchange.com

• Websites: fintech.ma, bitcoin.fr

• Slack groups: CryptoFR, BlockChainBelgium, fintech.ma

• Network monitors: blockchain.info, ethstats.net

@sarbogast @eloudsa


http://steemit.com

http://bitcoin.stackexchange.com

http://ethereum.stackexchange.com

http://fintech.ma

http://bitcoin.fr

http://fintech.ma

http://blockchain.info

http://ethstats.net

Getting started with blockchain development

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• Bitcoin: • Mastering Bitcoin, the book: https://bitcoin.org/en/developer-guide • https://github.com/bitcoinbook/bitcoinbook

• Ethereum: • https://ethereum.org/ • The smart contract language, Solidity: https://solidity.readthedocs.io • The build tool, Truffle: http://truffle.readthedocs.io/ • The developer friendly client, Geth: https://github.com/ethereum/go-ethereum/wiki/

geth

@sarbogast @eloudsa


https://bitcoin.org/en/developer-guide

https://github.com/bitcoinbook/bitcoinbook

https://ethereum.org/

https://solidity.readthedocs.io

http://truffle.readthedocs.io/

https://github.com/ethereum/go-ethereum/wiki/geth

https://github.com/ethereum/go-ethereum/wiki/geth

A few pieces of advice

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• If you want to go for production quickly, your contracts don't need loops, and you have patience have a look at Bitcoin development first

• Documentation and articles get outdated really quickly, so be prepared to tinker a lot and figure things out as you go

• Development tools are still very very raw (Jetbrains, if you're listening to this…)

• Forget about mobile apps for now, light wallets are not ready yet

@sarbogast @eloudsa


One more thing…

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@sarbogast @eloudsa


@sarbogast @eloudsa


beta.chainskills.com

http://beta.chainskills.com

Engineering

Why you should be interested in the blockchain