Blockchain

Blockchain is the technology that makes Bitcoin, Ethereum, and thousands of other cryptocurrencies possible. At its simplest, it's a database — but unlike any database before it, no single person or organization controls it, and once data is written, it cannot be altered or deleted.

How Blockchain Works

Imagine a spreadsheet that's duplicated across thousands of computers worldwide. When someone makes a transaction, every computer updates its copy simultaneously. These transactions are grouped into "blocks" — each containing a batch of recent transactions, a timestamp, and a cryptographic link (hash) to the previous block. This chain of blocks creates an immutable record.

The key innovation: each block's hash depends on the previous block's hash. If anyone tries to change a past transaction, all subsequent hashes would change — and every other node in the network would immediately detect the tampering. To alter the blockchain, you'd need to control 51%+ of the network's computing power simultaneously. For Bitcoin, that would require more electricity than most countries consume.

Blocks and Chains

A block typically contains: a list of transactions (who sent what to whom), a timestamp, a nonce (a number used in mining to find a valid hash), the hash of the previous block (creating the "chain"), and the block's own hash (a unique fingerprint). Bitcoin blocks are created every ~10 minutes and can hold about 2,000-3,000 transactions. Ethereum blocks are created every ~12 seconds.

Types of Blockchains

• Public blockchains (Bitcoin, Ethereum) — anyone can join, read, and write. Fully decentralized. Secured by consensus mechanisms like Proof of Work or Proof of Stake
• Private blockchains (Hyperledger, R3 Corda) — permissioned networks controlled by organizations. Faster but less decentralized. Used by banks and enterprises
• Consortium blockchains — semi-decentralized, controlled by a group of organizations. Used for supply chain management and industry collaboration
• Layer 2 blockchains (Lightning Network, Arbitrum) — built on top of Layer 1 blockchains to improve speed and reduce fees

Use Cases Beyond Cryptocurrency

• Supply chain tracking — Walmart tracks food from farm to shelf using blockchain, reducing contamination response from 7 days to 2 seconds
• Digital identity — self-sovereign identity lets individuals control their own data without relying on corporations
• Voting — blockchain-based voting systems ensure transparency and prevent fraud
• Healthcare — medical records stored on blockchain give patients control and enable secure sharing between providers
• Real estate — tokenized property enables fractional ownership and instant transfers

Every cryptocurrency traded on EIDEX runs on a blockchain. Understanding blockchain technology helps you evaluate projects and make informed investment decisions.