Clear DefinitionsImmutability
1 min read
Pronunciation
[ih-myoo-tuh-bil-i-tee]
Analogy
Imagine writing in permanent ink on a page of a book, where everyone has an identical copy of that book. Once the ink dries, you cannot erase or modify what's written—you can only add new pages. Everyone will immediately notice if someone tries to tear out or alter a page in their copy.
Definition
The property of blockchain data that prevents it from being altered or deleted once it has been recorded and confirmed. Records become permanent and unchangeable once added to the blockchain.
Key Points Intro
Immutability creates a tamper-evident historical record of all transactions.
Key Points
Achieved through cryptographic hashing that links blocks together.
Any attempt to alter past data would require recalculating all subsequent blocks.
Requires consensus from the majority of the network to validate any changes.
Creates a verifiable audit trail for digital assets and interactions.
Example
When a Bitcoin transaction is confirmed in a block and several more blocks are added afterward, it becomes practically impossible to reverse or modify that transaction due to the computational resources required to rewrite the blockchain's history.
Technical Deep Dive
Immutability is probabilistic rather than absolute. As more blocks are built on top of a transaction (known as confirmations), the likelihood of that transaction being altered approaches zero. This is because altering historical data would require controlling enough computing power to recalculate all subsequent blocks faster than the honest network can add new blocks.
Security Warning
Smaller blockchains with less distributed hashing power are more vulnerable to 51% attacks that could potentially rewrite recent history. Always wait for multiple confirmations before considering high-value transactions final.
Caveat
Some blockchain implementations do allow for data to be modified under specific conditions or through governance processes, representing a trade-off between absolute immutability and practical functionality.
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