Une description technique de la blockchain.

1. Bienvenue !
@BdxCoin

2. Blockchain 101
Some tech flavors

3. ● Yay, crypto !
● Bitcoins don’t exist
● The blockchain is Mining
Summary

4. because in cryptocurrency, there’s crypto
Yay, crypto !

5. What is a hash ?
data1
data2
data1
5b41362bc82b7f3d56e...
5b41362bc82b7f3d56e...
d98cf53e0c8b77c14a9...SHA-256

6. What is a Bitcoin address ?
Private key Public key
Wallet
Allows to spend
Bitcoins :
Keep it secret !
Used to receive
Bitcoins :
You can share it !

7. “My whole life is a lie” - everyone in this room
Bitcoins don’t exist

8. ● There is no “bitcoin balance” stored
● Balances are computed from
transaction history
Bitcoins are transactions

9. Transaction : simplified
transaction
input output
fee
5 BTC 4.99 BTC
0.01 BTC

10. Transaction : less simplified
transaction ID
inputs output
fee
4 BTC 4.5 BTC
0.01 BTC
1 BTC
change
0.49 BTC

11. Transactions are grouped in blocks
transaction
transaction
transaction
transaction
Block
reward transaction

12. Blocks are chained in...
block
block
block
block
Blockchain !

13. time to turn off your heating system
Blockchain is mining

14. ● Need to make sure blocks are not
altered
● -> Let’s hash them !
Avoiding double spending

15. ● Hash the block to make sure it
wasn’t altered
● Include hash of the previous block
to make sure all the previous blocks
weren’t altered !
Block hashing

16. Block hashing
block
hash
block
hash

17. A simple hash is very fast to make :
one can fork the blockchain
Problem :

18. ● Let’s add some difficulty
● The block hash must meet certain
requirements
● Difficulty regulates block
generation speed
Proof of Work

19. ● Miners try to find a valid block hash
● The first to find it broadcasts it, and
gets the reward + the fees
● Without miners, no blockchain
Mining

20. ● bitcoin.pdf
● en.bitcoin.it/wiki/Category:Technical
● live blockchain monitor : blockchain.info
More tech details ?

21. Thank you !