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Introduction to the
Blockchain technology
Blockchain Vlaanderen Meetup #2
April, 18th 2016 - KBC Boerentoren Antwerpen
1. What is Blockchain?
2. How does Blockchain work?
3. And what are smart contracts?
Intro into blockchain
How does Blockchain work,
explained using the Bitcoin
blockchain
Meet Peter and Mary
Peter Mary
Only identified by their private key
Private key:
MHQCAQEEIDlbC…dPiE
Laz5K4+PO4w==
Private key:
MHQCAQEEIMxR…jHiHBI
JyuCtGkdJzw==
Peter Mary
And the public address of their wallet
Private key:
MHQCAQEEIDlbC…dPiE
Laz5K4+PO4w==
Private key:
MHQCAQEEIMxR…jHiHBI
JyuCtGkdJzw==
Address:
19jgcudmDT…
vXfJd47yjLev
Address:
1VDQ5BJfRC
…
27SsKfUrgdaG
Peter Mary
Since the blockchain is a ledger, it knows the balance of those
wallets
Private key:
MHQCAQEEIDlbC…dPiE
Laz5K4+PO4w==
Private key:
MHQCAQEEIMxR…jHiHBI
JyuCtGkdJzw==
Address:
19jgcudmDT…
vXfJd47yjLev
Address:
1VDQ5BJfRC
…
27SsKfUrgdaG
Peter Mary
Mary constructs a transaction to send 10BTC to
Peter
Peter Mary
send 10 BTC
from 1VDQ5BJfRC…27SsKfUrgdaG
to 19jgcudmDT…vXfJd47yjLev
Address:
19jgcudmDT…
vXfJd47yjLev
Address:
1VDQ5BJfRC
…
27SsKfUrgdaG
And signs it with her private key
Peter Mary
send 10 BTC
from 1VDQ5BJfRC…27SsKfUrgdaG
to 19jgcudmDT…vXfJd47yjLev
Address:
19jgcudmDT…
vXfJd47yjLev
Address:
1VDQ5BJfRC
…
27SsKfUrgdaG
Private key:
MHQCAQEEIMxR…jHiHBI
JyuCtGkdJzw==
The transaction is sent to the
network and propagates into
the transaction pool of each node
Miners start to create a candidate
block
Candidate Block
Transaction Pool
Validate and sort the transactions into
a candidate block, no larger than the
maximum blocksize
A block contains the transactions, plus the Merkle root
Candidate Block
Transaction Pool
Merkle root ~
hash of all transactions
in the block
And includes the hash of the previous block to chain them
together
Candidate Block
Transaction Pool
Merkle root ~
hash of all transactions
in the block
Hash of the
previous block
Solving the proof of work puzzle, finding the nonce
Transaction Pool Proof of work
Candidate Block
After solving the puzzle, the result is sent back to the network
Transaction Pool Proof of work
Transmit the block
to the network
Candidate Block
And start again…
Transaction Pool Proof of work
Transmit the block
to the network
Candidate Block
Challenges of a distributed network:
forking
Blockchain
19:15:10 - New block found on top of “green”!
A fork in the making
19:15:11 - New block found on top of “green”!
Blockchain
The chain has forked!Blockchain
Some miners are mining on top of “red”, some on top of “yellow”Blockchain
19:25:13 - New block found on top of “yellow”!
BlockchainA new block has been mined
Order has been restored, all is
well…
Blockchain
Forking over one/two blocks is extremely rare.
Transactions are considered secure after 6 blocks
And what are smart contracts?
Peter, now using a wallet with Ether…
Address:
19jgcudmDT…
vXfJd47yjLev
Peter
… interacts with a “living” piece of software in the
blockchain
Private key:
MHQCAQEEIDlbC…dPiE
Laz5K4+PO4w==
Address:
19jgcudmDT…
vXfJd47yjLev
Address:
1VDFGSJfRC
…
27SsKfDhdiF
Peter
Turing complete
programming language
e.g. car lease
And pays for the processing power using “gas”
Private key:
MHQCAQEEIDlbC…dPiE
Laz5K4+PO4w==
Address:
19jgcudmDT…
vXfJd47yjLev
Address:
1VDFGSJfRC
…
27SsKfDhdiF
Peter
Turing complete
programming language
Gas
Not just human to smart contract, but also between contracts
Private key:
MHQCAQEEIDlbC…dPiE
Laz5K4+PO4w==
Address:
19jgcudmDT…
vXfJd47yjLev
Peter
Questions?

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Intro into blockchain

  • 1. Introduction to the Blockchain technology Blockchain Vlaanderen Meetup #2 April, 18th 2016 - KBC Boerentoren Antwerpen
  • 2. 1. What is Blockchain? 2. How does Blockchain work? 3. And what are smart contracts?
  • 4. How does Blockchain work, explained using the Bitcoin blockchain
  • 5. Meet Peter and Mary Peter Mary
  • 6. Only identified by their private key Private key: MHQCAQEEIDlbC…dPiE Laz5K4+PO4w== Private key: MHQCAQEEIMxR…jHiHBI JyuCtGkdJzw== Peter Mary
  • 7. And the public address of their wallet Private key: MHQCAQEEIDlbC…dPiE Laz5K4+PO4w== Private key: MHQCAQEEIMxR…jHiHBI JyuCtGkdJzw== Address: 19jgcudmDT… vXfJd47yjLev Address: 1VDQ5BJfRC … 27SsKfUrgdaG Peter Mary
  • 8. Since the blockchain is a ledger, it knows the balance of those wallets Private key: MHQCAQEEIDlbC…dPiE Laz5K4+PO4w== Private key: MHQCAQEEIMxR…jHiHBI JyuCtGkdJzw== Address: 19jgcudmDT… vXfJd47yjLev Address: 1VDQ5BJfRC … 27SsKfUrgdaG Peter Mary
  • 9. Mary constructs a transaction to send 10BTC to Peter Peter Mary send 10 BTC from 1VDQ5BJfRC…27SsKfUrgdaG to 19jgcudmDT…vXfJd47yjLev Address: 19jgcudmDT… vXfJd47yjLev Address: 1VDQ5BJfRC … 27SsKfUrgdaG
  • 10. And signs it with her private key Peter Mary send 10 BTC from 1VDQ5BJfRC…27SsKfUrgdaG to 19jgcudmDT…vXfJd47yjLev Address: 19jgcudmDT… vXfJd47yjLev Address: 1VDQ5BJfRC … 27SsKfUrgdaG Private key: MHQCAQEEIMxR…jHiHBI JyuCtGkdJzw==
  • 11. The transaction is sent to the network and propagates into the transaction pool of each node
  • 12. Miners start to create a candidate block Candidate Block Transaction Pool Validate and sort the transactions into a candidate block, no larger than the maximum blocksize
  • 13. A block contains the transactions, plus the Merkle root Candidate Block Transaction Pool Merkle root ~ hash of all transactions in the block
  • 14. And includes the hash of the previous block to chain them together Candidate Block Transaction Pool Merkle root ~ hash of all transactions in the block Hash of the previous block
  • 15. Solving the proof of work puzzle, finding the nonce Transaction Pool Proof of work Candidate Block
  • 16. After solving the puzzle, the result is sent back to the network Transaction Pool Proof of work Transmit the block to the network Candidate Block
  • 17. And start again… Transaction Pool Proof of work Transmit the block to the network Candidate Block
  • 18. Challenges of a distributed network: forking Blockchain
  • 19. 19:15:10 - New block found on top of “green”! A fork in the making 19:15:11 - New block found on top of “green”! Blockchain
  • 20. The chain has forked!Blockchain
  • 21. Some miners are mining on top of “red”, some on top of “yellow”Blockchain
  • 22. 19:25:13 - New block found on top of “yellow”! BlockchainA new block has been mined
  • 23. Order has been restored, all is well… Blockchain Forking over one/two blocks is extremely rare. Transactions are considered secure after 6 blocks
  • 24. And what are smart contracts?
  • 25. Peter, now using a wallet with Ether… Address: 19jgcudmDT… vXfJd47yjLev Peter
  • 26. … interacts with a “living” piece of software in the blockchain Private key: MHQCAQEEIDlbC…dPiE Laz5K4+PO4w== Address: 19jgcudmDT… vXfJd47yjLev Address: 1VDFGSJfRC … 27SsKfDhdiF Peter Turing complete programming language e.g. car lease
  • 27. And pays for the processing power using “gas” Private key: MHQCAQEEIDlbC…dPiE Laz5K4+PO4w== Address: 19jgcudmDT… vXfJd47yjLev Address: 1VDFGSJfRC … 27SsKfDhdiF Peter Turing complete programming language Gas
  • 28. Not just human to smart contract, but also between contracts Private key: MHQCAQEEIDlbC…dPiE Laz5K4+PO4w== Address: 19jgcudmDT… vXfJd47yjLev Peter