Most of us rely on central authorities. Banks track our money, companies manage our data, and governments keep our records. A blockchain records and verifies information in a different way: many independent computers keep the same shared record, and no single company or government runs it. This is the idea behind blockchain technology.
A Simple Way to Understand It
To grasp blockchain, imagine a notebook shared between a group of people. Every time someone writes something down, like a payment or an agreement, the group checks it and adds it to a new page. Each new page carries a reference to the page before it, so the pages form a chain. Everyone keeps a copy of the notebook, so nobody can quietly rewrite an old page without the others noticing.
A blockchain works the same way. The notebook is digital, and its copies are held by thousands of independent computers that follow the same rules to keep them matching.1
How Blockchain Works
A blockchain is made up of individual blocks. Each block bundles a group of transactions and stores a cryptographic link back to the block before it, which keeps the blocks in order.2 On Cardano, a new block is added roughly every 20 seconds.3
That link is what makes the record hard to change. If someone edits an old block, the reference stored in the next block no longer matches, and every block after it breaks. Anyone can check the full history and spot the edit.3 On Bitcoin, an attacker would also have to redo the computing work for that block and for every block after it.4
Instead of sitting on one company's server, the record is copied across a global network of computers called nodes. When a node receives a new block, it verifies the transactions inside before sharing the block with other nodes.3 To agree on who adds the next block, the network follows a set of rules called a consensus protocol. There are two main kinds:
- Proof of work. Computers called miners race to solve a computing puzzle, and whoever solves it first adds the next block. Bitcoin works this way.5
- Proof of stake. The protocol picks the next block producer based on how much of the network's currency is staked with it. Cardano works this way.6
Either way, no middleman has to confirm a payment or who owns what. Traditionally we trust institutions to manage important data. A blockchain moves that trust to public rules and to computers that check each other's work.1,3
Real-World Applications
Blockchain is best known as the technology behind cryptocurrencies, but a shared record that no single party controls is useful elsewhere too.
- Supply chains. Each step of a product's journey can be logged on a public chain, where it can't be quietly edited later. For example, the Cardano Foundation worked with Georgia's National Wine Agency on a program that records batches of Georgian wine and their certificates on Cardano, starting with the Bolnisi region, so a buyer can check where a bottle came from.7 Adastack lists more supply chain projects.
- Finance. Smart contracts are pieces of code kept on a blockchain. When the agreed conditions are met, the code enforces the deal by itself, with no escrow agent.8 On Cardano, smart contracts run lending apps, stablecoins, and decentralized exchanges (DEXs),9 where people trade tokens from their own wallets.10
- Digital identity. A decentralized identifier (DID) is an ID that belongs to you rather than to a platform. No central registry issues it, and the record behind it lives on a blockchain rather than in one company's database.11 See Adastack's identity category for examples.
- Voting. Changes to Cardano's rules and spending from its treasury are settled by votes recorded on the chain. ADA holders vote directly or through representatives they choose, and stake pool operators and a constitutional committee act as checks on each decision.1 What is Cardano governance explains how it works.
Blockchain in Action
Bitcoin, described in a 2008 white paper by the pseudonymous Satoshi Nakamoto, was the first widely adopted cryptocurrency.12 It showed that people could send digital money to each other online without a bank in the middle.4
Later blockchains built on that idea. Cardano went live in September 2017. People use it to make payments in ADA, its currency, issue their own tokens, run applications, and vote on upgrades.1 Its consensus protocol, Ouroboros, is a form of proof of stake that was published and reviewed by other researchers before Cardano used it.1 Cardano has never used mining, so stake pools run on standard servers rather than specialized mining machines.1
You can take part without running any of that hardware. Staking on Cardano means delegating your ADA to a stake pool, a server that produces blocks. The ADA stays in your wallet, and you earn a share of the rewards the pool collects.13 To get started, see how to stake ADA on Cardano.
Learn More
- How Cardano Works: Step-by-step explainer on the Cardano website covering slots, blocks, tokens, smart contracts and upgrades
- Blockchain Fundamentals: Self-paced 90-minute beginner course from the Cardano Foundation's Cardano Academy (free account required)
- Cardano glossary: Plain-English definitions of common Cardano terms
- Block explorers: Tools for looking up real Cardano blocks, transactions, and addresses
