20180711 blockchain presentation in Blockchain&Dapps
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I explain Blockchain concept with a simple blockchain which made by nodeJS.
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20180711 blockchain presentation in Blockchain&Dapps
- 2. Kenneth Hu • I am a software developer , not trader. • I am enthusiast, not expert. • Ethereum, Bitcoin, AR, ChatBot • Email: Kenneth.hu@Hotmail.com • Blockchain&Dapps meetup • Singapore IOTA meetup
- 4. What is transaction? Kenneth Alice $30 SGD Transaction: “ is a transfer of value”
- 5. Ledger : “a collection of financial accounts or transactions” Ledger Kenneth Alice #30 Amy Jen #50 Immutable : The ledger cannot be changed. Ever! What is ledger?What is Immutable?
- 6. What is block? BLOCK Block Header Hash of previous block header Merkle root Timestamp Nonce Transactions Block : A block records some or all of the most recent transactions. Thus a block is like a page of a ledger or record book.
- 7. Block header BLOCK Header Hash of previous block header Merkle root Timestamp Nonce • Hash of previous block header • Timestamp : It indicates when the block was created. • Merkle root : hash-based data structure that is a generalization of the hash list. • Nonce :Counter used for the Proof of Work algorithm. Each time you mine, the nonce increases by 1 .
- 8. BLOCK 1 HEADER Hash of previous block header Merkle root Block 1 transactions BLOCK 2 HEADER Hash of previous block header Merkle root Block 2 transactions BLOCK 3 HEADER Hash of previous block header Merkle root Block 3 transactions Blockchain
- 9. • Creating the candidate block Mining HASHING ( SHA256 ) Block’s Block header data Hash of previous block header Merkle root Timestamp Nonce No : ( Increment the nonce by 1. Hash again! Is hash (A8SBERA….) lower than the target? (check the leading zeros) YES! Problem Solved. Proof of Work
- 10. • Block header hash is less than the target • Block size is within acceptable limits • Block timestamp is less than two hours in the future. • The first transaction is a coinbase transaction ( and only the first ) • The coinbase transaction has a valid reward. • All transactions within the blocks are valid ( also have a checklist on their own ) Source : https://dev.to/damcosset/blockchain-what-is-mining-2eod Validate the new block
- 11. Node Time David Sandra 5 BTC Brian List 3.02 BTC Mary Sandra 10 BTC Lisa Sandra 10 BTC Sandra David 10 BTC BLOCK #187 Block ID 0x0235de9a6 Previous Block 0x6e257071cec Transactions Lisa Sandra 10 BTC Brian List 5 BTC Mary Sandra 10 BTC …… ……… .. BTC BLOCK #186 Block ID 0x6e257071cec Previous Block 0x1dcc4de8dec Transactions BLOCK #186 Block ID 0x6e257071cec Previous Block 0x1dcc4de8dec Transactions BLOCK #186 Block ID 0x6e257071cec Previous Block 0x1dcc4de8dec Transactions BLOCK #186 Block ID 0x6e257071cec Previous Block 0x1dcc4de8dec Transactions Blockchain network Blockchain
- 12. What does “distributed” mean ? Distributed: A distributed ledger is a database that is consensually shared and synchronized across network spread across multiple node Ledger Ledger Ledger Ledger Ledger Ledger node node node nodenode node
- 13. Demo
- 14. Ledger Transaction/Mining/Sync Ledger Node 3 Node 1 Node 2 Node 4 Ledger Ledger • 1. submit a transaction • 2. Mining & Validation • 3. Sync to other node
- 15. Ledger Consensus Ledger Node 3 Node 1 Node 2 Node 4 Ledger Ledger Ledger Node 5 • 1. run new node (node 5) • 2. join the network • 3. Sync to other node