In a blockchain system, each block’s integrity is validated through the use of a cryptographic hash. Here’s how it works:
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Data Integrity: Each block contains data, such as transactions, which are hashed into a unique string. This hash acts as a checksum to detect any unauthorized modifications. Any alteration in the data will result in a different hash.
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Merkle Tree Structure: Transactions within a block are individually hashed and combined hierarchically into a single root hash (the Merkle Root). This structure ensures that any change in even one transaction will alter the root hash, making it impossible to tamper with transactions without detection.
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Cryptographic Properties: The hash function used is deterministic, collision-resistant, and one-way. This means the same input always produces the same hash, making it highly unlikely for different inputs to share a hash (collision resistance). Additionally, hashes are pre-image resistant, preventing reverse-engineering of original data from its hash.
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Security Against Tampering: In blockchains like Bitcoin, each block’s hash is part of the next block’s header. Altering a previous block changes its hash, which in turn affects all subsequent blocks’ hashes, creating a computationally intensive task to alter multiple blocks and undermining network consensus mechanisms.
In essence, the block hash ensures data integrity by validating that the contents have not been altered since the hash was created, making blockchain systems robust against tampering.