Structure of a Single Block in a Blockchain
Here’s a conceptual example of how a blockchain might look, explained in simple terms:
Structure of a Single Block in a Blockchain:
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**Block #12345:**
- **Block Hash**: 00000000000000000123456789abcdef
- **Previous Block Hash**: 00000000000000000123456789abcdee
- **Timestamp**: 2025-02-02 16:42:00
- **Nonce**: 123456
- **Transaction List**:
- **Transaction 1**:
- **Sender**: Alice
- **Receiver**: Bob
- **Amount**: 10 BTC
- **Transaction 2**:
- **Sender**: Bob
- **Receiver**: Charlie
- **Amount**: 5 BTC
- **Merkle Root**: 0123456789abcdef0123456789abcdef
Explanation:
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Block Hash: A unique identifier for this block, derived from all the data within the block including the transactions, the previous block’s hash, timestamp, and nonce.
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Previous Block Hash: The hash of the block that came before this one, which creates the chain. Changing any data in any block would change this hash, rendering the entire chain invalid from that point forward.
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Timestamp: When the block was created.
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Nonce: A number used only once, used in mining to find a hash that meets the network’s difficulty criteria.
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Transaction List: The records of exchanges or data transfers that are included in this block. Here, I’ve shown two example transactions.
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Merkle Root: A hash of all the transactions in the block, providing a way to verify the integrity of the transaction data without listing all transactions.
Visual Representation:
Imagine this block as one link in a chain, where:
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Each block is connected to the next one via the hash of the previous block.
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The chain extends back to the ‘genesis block‘ or the first block in the blockchain.
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If you altered any data in any block, the hash of that block would change, which would mean all subsequent blocks would no longer be valid because their Previous Block Hash would no longer match.
This structure ensures security because altering any block would require re-mining that block and all subsequent blocks to maintain the chain’s integrity, which is computationally infeasible in well-secured blockchains due to the amount of computing power needed.
