This slidedeck was used at the second Blockchain Vlaanderen meetup in Antwerp. It was given as a general introduction into Blockchain to enable newcomers to follow the presentations that followed.

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

29. Questions?