How exactly does solving nounce verify the transaction. or how are both of them interrelated.how does my transaction gets verified.
2 Answers
Simply, it doesn't. The hashing puzzle is only needed for all nodes to agree on a common value. Once a block is found it is propagated through the network. If the nounce is valid AND if the transactions in the blocks are valid then the block is accepted into the blockchain. A transaction is valid if:
- each transaction input matches a previous transaction output.
- they are reedemed by their legitimate owners
- the sum of values of all transaction outputs is less than or equal to the sum of the values of all inputs.
This verification is performed by bitcoin nodes. A miner is not incentivized to include invalid transactions in their blocks as they will invalidate the entire block (thus preventing the miners to obtain the coinbase reward).
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So i was watching this video. youtube.com/watch?v=9-9_v1wSPBQ&t=333s In reference to this. once this data is broadcasted to each node and miners. all of them will first verify the transaction by matching data Alice sent vs that in leadger. and at last will agree on majority. But then why do Alice have to send his own previous transactions information couldnt that be done directly by nodes?? Feb 20, 2018 at 18:18
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Bitcoin's core philosophy is privacy and decentralization. Letting a node identify users is against the specification of the protocol itself. Furthemore, Bitcoin users don't have any identifiable accounts, instead they have addresses that can be generated easily by several softwares. Every user has about 215,000,000,000,000,000,000,000,000,000,000,000,000 addresses per capita.(2.15 x 10^38) Source. So it is impossible for a node to know every addresses-user association.– berrurFeb 22, 2018 at 11:35
Nounce is per block and not per transaction. Each block contains many transactions.
Blockchain is the history of transactions. And all transactions are verified against that history. If history says you have 2 BTC, then your transaction of sending 2 BTC to your friend is valid and your transaction of sending 3 BTC to your friend is invalid.
Every full node contains a full history of transactions called Blockchain. So every node can validate every transaction and block easily. Nounce is a way to reach consensus about the state of that blockchain.
