Block Chain - Immutability

Immutability is the property of a blockchain that makes recorded data permanent and unchangeable once confirmed.

Core Explanation (Exam-Focused)

1. No Data Alteration
   Transactions cannot be modified or deleted after confirmation.

2. Cryptographic Hash Linking
   Each block contains the hash of the previous block; altering one block breaks the chain.

3. Consensus Protection
   Any change would require controlling a majority of network power, which is impractical.

4. Distributed Storage
   Multiple nodes hold copies of the ledger, preventing unilateral changes.

5. Tamper Resistance
   Unauthorized modifications are immediately detectable.

Role in Blockchain

• Guarantees data integrity

• Builds trust without intermediaries

• Ensures reliable transaction history

Practical Example

• A confirmed Bitcoin transaction cannot be reversed or edited.

Limitation

• Errors cannot be corrected; new transactions must be added to offset mistakes.

One-Line Definition (Exam Use)

Immutability is the characteristic of blockchain that ensures once data is recorded and confirmed, it cannot be altered or erased.