Immutable Ledger
An immutable ledger is a specialized data structure that is designed to be permanent and unalterable.
Properties: 1. Append-only. 2. Sequentially linked. 3. Cryptographically signed. 4. Auditable. Use cases: Cryptocurrency, Supply Chain tracking, Legal records.
graph LR
Center["Immutable Ledger"]:::main
Pre_operating_systems["operating-systems"]:::pre --> Center
click Pre_operating_systems "/terms/operating-systems"
Pre_virtualization["virtualization"]:::pre --> Center
click Pre_virtualization "/terms/virtualization"
Rel_secure_enclaves["secure-enclaves"]:::related -.-> Center
click Rel_secure_enclaves "/terms/secure-enclaves"
Rel_virtual_private_cloud_vpc["virtual-private-cloud-vpc"]:::related -.-> Center
click Rel_virtual_private_cloud_vpc "/terms/virtual-private-cloud-vpc"
Rel_evm_sandboxing["evm-sandboxing"]:::related -.-> Center
click Rel_evm_sandboxing "/terms/evm-sandboxing"
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🧒 Explain Like I'm 5
Imagine a giant diary where you write with a permanent marker that can never be erased. Every time you write on a new page, you have to describe exactly what was on the page before it. If you try to tear out a page or change an old one, everyone will see that the new pages don't match the old ones anymore. That's an immutable ledger.
🤓 Expert Deep Dive
Technically, immutability is achieved through 'Hash Chaining'. Each block of data contains a cryptographic hash of the previous block (forming a 'Merkle Root' or 'Merkle [Tree](/en/terms/merkle-tree)'). This creates a 'High Integrity' audit trail. In centralized systems, this is used in 'Append-Only' databases like Amazon QLDB. In decentralized systems (Blockchain), it is combined with a 'Consensus Mechanism' (like Proof of Work). Changing history would require re-calculating the hashes for all subsequent blocks and convincing the majority of the network to accept the fake version—a feat that is computationally and economically infeasible for secure networks.