---
id:"kb-2026-00256"
title:"Blockchain Technology"
schema_type:"TechArticle"
category:"computer-science"
language:"en"
confidence:"high"
last_verified:"2026-05-22"
generation_method: "human_only"
ai_models:["claude-opus"]
derived_from_human_seed:true


known_gaps:
  - "Sources reconstructed during quality audit; primary source details were corrupted during batch generation"

completeness: 0.88
ai_citations:
  last_citation_check:"2026-05-22"
primary_sources:
- title: "ACM Digital Library"
    type: "repository"
    year: 2026
    url: "https://dl.acm.org/"
    institution: "ACM"
secondary_sources:
  - title: "ACM Digital Library"
    type: "repository"
    year: 2026
    url: "https://dl.acm.org/"
    institution: "ACM"
---

## TL;DR

Blockchain is a distributed, immutable ledger where transactions are grouped into blocks, cryptographically linked in a chain. Satoshi Nakamoto's Bitcoin (2009) was the first. Consensus mechanisms: Proof-of-Work (Bitcoin, mining), Proof-of-Stake (Ethereum since 2022, validators stake). Blockchain = decentralized trust without intermediaries.

## Core Explanation

Block: transactions + timestamp + hash of previous block. Changing any past block invalidates all subsequent hashes — computationally infeasible. Merkle tree: efficiently verify transaction inclusion. Smart contracts (Ethereum): code stored on blockchain, executed by validators. Beyond currency: supply chain, digital identity, voting, DeFi. Public vs. private (permissioned) blockchains. 51% attack: controlling majority of hash power/stake enables double-spending.

## Further Reading

- [Bitcoin: A Peer-to-Peer Electronic Cash System (Nakamoto, 2008)](undefined)