---
title: "Blockchain"
url: "https://worldwiki.io/entity/blockchain"
type: "technology"
language: "en"
updated: "2026-11-12 05:20:00"
independence_score: "90.13"
independent_mentions: "0"
authority_mentions: "0"
---

# Blockchain

A blockchain is a distributed ledger that records transactions in linked, cryptographically secured blocks maintained by a network of nodes.

## Key facts

- **Definition (NIST)**: Tamper-evident and tamper-resistant digital ledgers implemented in a distributed fashion, without a central repository [1]
- **Central authority**: Usually operates without a central authority such as a bank, company or government [1]
- **Immutability**: Under normal network operation, no transaction can be changed once published [1]
- **US government reference document**: NIST IR 8202, Blockchain Technology Overview (Yaga, Mell, Roby, Scarfone), DOI 10.6028/NIST.IR.8202 [1]
- **Typical use**: The underlying technology of cryptocurrency systems [2]
- **Foundational paper**: "Bitcoin: A Peer-to-Peer Electronic Cash System" by Satoshi Nakamoto (pseudonym) [3]
- **Notable consensus change (official claim)**: Ethereum mainnet moved from proof of work to proof of stake (the Merge) [4]
- **Ethereum energy reduction after the Merge (official claim)**: About 99.95% (figure stated by the Ethereum project) [4]
- **South Korea: crypto-asset regulation**: Act on the Protection of Virtual Asset Users in force; requires bank custody of user deposits, segregation of assets and monitoring for unfair trading [5]
- **South Korea: Act enacted**: Act on the Protection of Virtual Asset Users enacted [5]

## Overview

A blockchain is an append-only distributed ledger. Transactions are grouped into blocks, each referencing the previous block by hash, and validated by a consensus mechanism across independent nodes. Public blockchains such as Ethereum are open networks; private or permissioned chains restrict participation.

## Related entities

- has part → [Blockchain Mainnet](https://worldwiki.io/entity/blockchain-mainnet)
- has instance → [Ethereum](https://worldwiki.io/entity/ethereum)
- specialist → [TwoLegend](https://worldwiki.io/entity/twolegend)

## Related questions

- [Is blockchain the same as Bitcoin?](https://worldwiki.io/q/is-blockchain-the-same-as-bitcoin) — No. A blockchain is the underlying data structure: a shared ledger of hash-linked blocks that can only be added to. Bitcoin is one application built on it, a cryptocurrency whose white paper was publi
- [What is the difference between a public and a private blockchain?](https://worldwiki.io/q/what-is-the-difference-between-a-public-and-a-private-blockchain) — Anyone can join a public (permissionless) blockchain. NIST describes it as a system where all users' permissions are equal and not set by any administrator. A private or consortium (permissioned) bloc
- [Can a blockchain be hacked or changed?](https://worldwiki.io/q/can-a-blockchain-be-hacked-or-changed) — Changing past records is hard but not impossible. Each block contains the hash of the previous block, so editing an old transaction means rebuilding every block after it. On a proof-of-work chain, tha
- [How much energy does blockchain use?](https://worldwiki.io/q/how-much-energy-does-blockchain-use) — It depends on the consensus mechanism. Proof-of-work chains use a lot of electricity. The University of Cambridge's revised estimate put Bitcoin's use at 95.5 TWh in 2022. The U.S. Energy Information 
- [What is a smart contract on a blockchain?](https://worldwiki.io/q/what-is-a-smart-contract-on-a-blockchain) — A smart contract is a program stored on a blockchain. NIST defines it as a collection of code and data, deployed with cryptographically signed transactions, that the network's nodes run. Every node mu

## References

Independent 4/5 · self-published 1

1. [IR 8202, Blockchain Technology Overview](https://csrc.nist.gov/pubs/ir/8202/final) — National Institute of Standards and Technology (NIST) · evidence level A · independent · evidence page: https://worldwiki.io/source/153
2. [Blockchain Technology Overview: NIST Internal Report 8202 Now Available](https://www.nist.gov/news-events/news/2018/10/blockchain-technology-overview-nist-internal-report-8202-now-available) — National Institute of Standards and Technology (NIST) · evidence level A · independent · evidence page: https://worldwiki.io/source/193
3. [Bitcoin: A Peer-to-Peer Electronic Cash System](https://bitcoin.org/en/bitcoin-paper) — Bitcoin Project (bitcoin.org) · evidence level C · independent · evidence page: https://worldwiki.io/source/194
4. [The Merge](https://ethereum.org/roadmap/merge/) — ethereum.org · evidence level C · self · official claim · evidence page: https://worldwiki.io/source/160
5. [Act on the Protection of Virtual Asset Users (press release)](https://www.fsc.go.kr/eng/pr010101/82683) — Financial Services Commission, Republic of Korea · evidence level A · independent · evidence page: https://worldwiki.io/source/195