Blockchain
By Menno — 13 years in crypto, 3 bear markets survived, zero paid promotions
Last updated: March 2026
A blockchain is a distributed, append-only database where data is organized into linked blocks and secured by cryptography. Once recorded, transactions cannot be altered — making it a trustless, permanent public ledger.
A blockchain is a database that is distributed across many computers and stores records (transactions) in linked groups called blocks. Each block contains a cryptographic reference to the previous block, creating an immutable chain of history.
Key properties: - Distributed: no single server stores all the data — thousands of nodes maintain identical copies - Immutable: once a block is added, changing it would require changing all subsequent blocks and controlling majority of the network - Transparent: all transactions are publicly visible (pseudonymous, not anonymous) - Trustless: you don't need to trust any single party — the cryptography and consensus mechanism enforce the rules
How a transaction gets recorded: 1. You broadcast a transaction (e.g., send 1 BTC) 2. Network nodes validate the transaction (do you have sufficient funds? is the signature valid?) 3. Miners/validators include it in a candidate block 4. Consensus is reached; the block is added to the chain 5. The transaction is now permanent and irreversible
Types of blockchains: - Public permissionless: anyone can join (Bitcoin, Ethereum) - Public permissioned: public but with restrictions - Private: controlled by a single organization (enterprise use cases) - Consortium: controlled by a group of organizations
Blockchain's innovation: it solved the "double-spend problem" — enabling digital assets to be transferred without the possibility of being spent twice, without needing a trusted central authority.
Frequently Asked Questions
Is blockchain the same as Bitcoin?
No. Blockchain is the underlying technology, and Bitcoin is the first application of it. Think of blockchain as the internet and Bitcoin as the first website. Ethereum, Solana, and thousands of other projects each run on their own blockchains.
Can blockchain data be deleted or altered?
In practice, no. Altering historical data would require controlling the majority of the network's consensus power and regenerating all subsequent blocks — an economically infeasible attack for established blockchains like Bitcoin and Ethereum. This immutability is one of blockchain's most valuable properties.
Related Terms
Consensus Mechanism
A consensus mechanism is the method a blockchain uses to achieve agreement among distributed nodes on the valid state of the ledger. The two dominant mechanisms are Proof of Work (Bitcoin) and Proof of Stake (Ethereum, Solana).
Proof of Work (PoW)
Proof of work is a consensus mechanism where miners compete to solve complex mathematical puzzles to validate transactions and create new blocks. Bitcoin uses proof of work, which is energy-intensive but highly secure.
Smart Contract
A smart contract is a self-executing program stored on a blockchain that automatically enforces the terms of an agreement when predefined conditions are met, without needing a middleman.
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