This article is general education about how the technology works. It is not investment, tax, legal or financial advice, and it does not suggest that anyone should buy, sell or hold any asset. Values of these assets can change sharply and people can lose all of what they put in.
The core idea
A cryptocurrency is a form of digital money whose records are kept by a network of computers rather than by a single bank or company. Ownership is tracked in a shared ledger, and cryptography is used to prove who is allowed to move which units. The result is a system in which people can send value to one another over the internet without a central operator approving each payment, at least in the design of the better-known systems.
Not every system works identically, and the word covers thousands of projects with different aims. The description below applies to the general model.
Ledgers, addresses and keys
Think of the ledger as a long list of transactions that many computers hold copies of. It does not store coins as objects. It records transfers, and a person’s balance is the result of adding up the transfers that involve their address.
Two linked pieces of data make this work:
- A public key or address, which is like an account identifier others can send to.
- A private key, a secret number that lets its holder authorize a transfer from that address.
A digital signature, made with the private key, shows the network that the owner approved a transaction without revealing the key itself. A wallet is the software or device that stores keys and creates these signatures. It is the keys, rather than any account with a company, that control the funds. For that reason, losing a private key can mean permanent loss of access, and anyone who obtains it can move the funds.
How a transaction is confirmed
When someone sends a payment, their wallet broadcasts it to the network. Participants gather pending transactions into groups called blocks and add them to the chain of earlier blocks, each linked to the last by a cryptographic fingerprint. This structure is a blockchain, which is explained further in the discussion of blockchain data storage. Altering an old block would change its fingerprint and break the links after it, which makes quiet tampering hard.
The network needs a way to agree on which block comes next, since computers may disagree or act dishonestly. This is the job of a consensus mechanism. Two broad families are common.
- Proof of work. Participants compete to solve a computational puzzle, and the winner adds the next block. The cost of the computation makes rewriting history expensive, but the process uses a lot of electricity.
- Proof of stake. Participants lock up some of the currency as a deposit and are chosen to add blocks, with penalties for cheating. It generally uses much less energy, with different security trade-offs.
Transactions are usually considered more settled as more blocks are added after them, so confirmation is a matter of degree rather than an instant switch.
Where new units come from
In some designs, new units are created as rewards for those who add blocks, following rules written into the software. Other systems issued their units at launch. Supply rules differ widely and can be changed only if the community running the software agrees, which is one reason governance in these projects can be contentious.
What people use them for
Uses reported include sending money across borders, holding a stored value outside the banking system, paying for goods at businesses that accept it, and running programs that execute automatically when conditions are met, often called smart contracts. How practical each use is depends on fees, speed, price swings and local rules. Many people hold these assets mainly as speculation, which carries high risk.
Some systems are designed to keep their value close to an ordinary currency, and these are often called stablecoins. Their stability depends on how they are backed and managed, and that arrangement can fail.
Risks to understand
- Price volatility. Values can rise and fall quickly and without clear cause.
- Scams and fraud. Fake giveaways, impersonation, fake exchanges and schemes promising guaranteed returns are common. Treat any promise of certain profit as a warning sign. The tactics overlap with phishing scams and social engineering.
- Irreversibility. A confirmed transfer to the wrong address or to a scammer generally cannot be undone, unlike a card payment that may be disputed.
- Custody risk. Leaving funds with an exchange means trusting that company; keeping them yourself means taking responsibility for protecting keys, ideally with multi-factor authentication on any related accounts.
- Software flaws. Bugs in wallets or in smart contract code have led to losses.
- Regulatory uncertainty. Rules on trading, reporting and taxes differ by country and change over time.
Privacy is not the same as anonymity
Many public ledgers show every transaction to anyone. Addresses are not names, but patterns of activity can sometimes be linked to a person, especially when they interact with a service that collects identity details. Some systems add features to hide more information. Those features raise their own policy debates.
How it differs from ordinary money
Bank money is a record in a bank’s database, backed by legal rules, deposit protections in many places and the ability to reverse some errors. Cryptocurrency shifts trust from institutions to software and the network, which removes some dependencies but also removes some protections. Neither is simply better; they make different trade-offs.
Questions to ask before engaging
Anyone considering involvement may find it useful to ask what problem the system solves, who controls the software and the supply, what happens if a key is lost, what the rules are locally, and how much loss they could tolerate. For decisions involving real money, qualified professionals who know the person’s circumstances are the right source of advice.