{"id":3,"slug":"blockchain","name":"Blockchain","alternate_names":["블록체인"],"aliases":[],"locale":"en","available_locales":["en"],"localized":false,"type":"technology","description":"A blockchain is a distributed ledger that records transactions in linked, cryptographically secured blocks maintained by a network of nodes.","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.","official_url":null,"image_url":null,"country":null,"region":null,"wikidata_id":null,"wikipedia_url":null,"verified":false,"scores":{"authority":72,"trust":0,"citation":0},"topic":{"slug":"blockchain-mainnet-development","name":"Blockchain"},"url":"https://worldwiki.io/entity/blockchain","facts":[{"id":91,"predicate":"definition","label":"Definition (NIST)","value":"Tamper-evident and tamper-resistant digital ledgers implemented in a distributed fashion, without a central repository","unit":null,"confidence":80,"valid_from":"2018-10-03","valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[153]},{"id":92,"predicate":"governance_model","label":"Central authority","value":"Usually operates without a central authority such as a bank, company or government","unit":null,"confidence":80,"valid_from":"2018-10-03","valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[153]},{"id":93,"predicate":"immutability_scope","label":"Immutability","value":"Under normal network operation, no transaction can be changed once published","unit":null,"confidence":80,"valid_from":"2018-10-03","valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[153]},{"id":94,"predicate":"reference_standard_us","label":"US government reference document","value":"NIST IR 8202, Blockchain Technology Overview (Yaga, Mell, Roby, Scarfone), DOI 10.6028/NIST.IR.8202","unit":null,"confidence":80,"valid_from":"2018-10-03","valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[153]},{"id":95,"predicate":"typical_use","label":"Typical use","value":"The underlying technology of cryptocurrency systems","unit":null,"confidence":80,"valid_from":"2018-10-03","valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[193]},{"id":96,"predicate":"origin_publication","label":"Foundational paper","value":"\"Bitcoin: A Peer-to-Peer Electronic Cash System\" by Satoshi Nakamoto (pseudonym)","unit":null,"confidence":80,"valid_from":null,"valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[194]},{"id":97,"predicate":"consensus_transition_example","label":"Notable consensus change (official claim)","value":"Ethereum mainnet moved from proof of work to proof of stake (the Merge)","unit":null,"confidence":60,"valid_from":"2022-09-15","valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[160]},{"id":98,"predicate":"energy_reduction_claim","label":"Ethereum energy reduction after the Merge (official claim)","value":"About 99.95% (figure stated by the Ethereum project)","unit":"percent","confidence":60,"valid_from":"2022-09-15","valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[160]},{"id":99,"predicate":"regulatory_status_kr","label":"South Korea: crypto-asset regulation","value":"Act on the Protection of Virtual Asset Users in force; requires bank custody of user deposits, segregation of assets and monitoring for unfair trading","unit":null,"confidence":80,"valid_from":"2024-07-19","valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[195]},{"id":100,"predicate":"regulatory_enactment_kr","label":"South Korea: Act enacted","value":"Act on the Protection of Virtual Asset Users enacted","unit":null,"confidence":80,"valid_from":"2023-07-18","valid_until":null,"verified_at":"2026-09-18 06:36:32","source_ids":[195]}],"relations":[],"questions":[{"slug":"is-blockchain-the-same-as-bitcoin","question":"Is blockchain the same as Bitcoin?","intent":"informational","language":"en","short_answer":"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 published on 31 October 2008 and whose first block was mined on 3 January 2009. Other public blockchains, such as Ethereum, run smart contracts. Permissioned platforms such as Hyperledger Fabric are used by known groups of organisations and do not need a public cryptocurrency.","url":"https://worldwiki.io/q/is-blockchain-the-same-as-bitcoin"},{"slug":"what-is-the-difference-between-a-public-and-a-private-blockchain","question":"What is the difference between a public and a private blockchain?","intent":"informational","language":"en","short_answer":"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) blockchain requires every node and user to be granted permission, usually by an administrator or consortium. Public chains such as Bitcoin and Ethereum use proof of work or proof of stake. Permissioned chains such as Hyperledger Fabric can use lighter ordering protocols, because their participants are known.","url":"https://worldwiki.io/q/what-is-the-difference-between-a-public-and-a-private-blockchain"},{"slug":"can-a-blockchain-be-hacked-or-changed","question":"Can a blockchain be hacked or changed?","intent":"informational","language":"en","short_answer":"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, that would take control of most of the network's computing power, known as a 51% attack. On Ethereum's proof-of-stake chain, it would take at least half of the staked ETH, and attackers can lose that stake. Wallets, keys and smart contract code can also be attacked separately.","url":"https://worldwiki.io/q/can-a-blockchain-be-hacked-or-changed"},{"slug":"how-much-energy-does-blockchain-use","question":"How much energy does blockchain use?","intent":"informational","language":"en","short_answer":"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 Administration estimated that crypto mining made up 0.6% to 2.3% of U.S. electricity consumption. Proof-of-stake chains use far less. Ethereum's energy consumption fell by an estimated 99.95% when it switched to proof of stake in September 2022.","url":"https://worldwiki.io/q/how-much-energy-does-blockchain-use"},{"slug":"what-is-a-smart-contract-on-a-blockchain","question":"What is a smart contract on a blockchain?","intent":"informational","language":"en","short_answer":"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 must get the same result, and the result is recorded on the chain. Smart contracts can automate things like token issuance or escrow. The OECD notes that making sure the code is correct and resolving disputes remain open challenges.","url":"https://worldwiki.io/q/what-is-a-smart-contract-on-a-blockchain"}],"sources":[{"id":153,"title":"IR 8202, Blockchain Technology Overview","url":"https://csrc.nist.gov/pubs/ir/8202/final","publisher":"National Institute of Standards and Technology (NIST)","type":"government","publication_date":null,"accessed_at":"2026-10-06 18:00:47"},{"id":193,"title":"Blockchain Technology Overview: NIST Internal Report 8202 Now Available","url":"https://www.nist.gov/news-events/news/2018/10/blockchain-technology-overview-nist-internal-report-8202-now-available","publisher":"National Institute of Standards and Technology (NIST)","type":"government","publication_date":"2018-10-03","accessed_at":"2026-11-10 18:01:00"},{"id":194,"title":"Bitcoin: A Peer-to-Peer Electronic Cash System","url":"https://bitcoin.org/en/bitcoin-paper","publisher":"Bitcoin Project (bitcoin.org)","type":"official","publication_date":null,"accessed_at":"2026-11-10 18:01:01"},{"id":160,"title":"The Merge","url":"https://ethereum.org/roadmap/merge/","publisher":"ethereum.org","type":"official","publication_date":null,"accessed_at":"2026-11-09 18:01:21"},{"id":195,"title":"Act on the Protection of Virtual Asset Users (press release)","url":"https://www.fsc.go.kr/eng/pr010101/82683","publisher":"Financial Services Commission, Republic of Korea","type":"government","publication_date":null,"accessed_at":"2026-10-16 18:00:49"}],"providers":[{"slug":"twolegend","name":"TwoLegend","verified_level":"verified","sponsored":false,"featured":false,"country":"KR","city":"Seoul","url":"https://worldwiki.io/provider/twolegend"}],"published_at":"2026-09-14 12:40:21","updated_at":"2026-11-12 05:20:00","verified_at":null}