Digital currency and blockchain
Introduced| English | Meaning |
|---|---|
| digital currency/ˈdɪdʒɪtl ˈkʌrənsi/ | Money or monetary value represented electronically; it need not be a decentralised cryptocurrency. |
| blockchain/ˈblɒktʃeɪn/ | A digital ledger — a shared record of every transaction , copied across many computers, so no one person controls it and it is very hard to change. |
| digital ledger/ˈdɪdʒɪtl ˈledʒə/ | An electronic record of transactions or changes; it need not use a blockchain. |
| transaction/trænˈsækʃn/ | An exchange or recorded operation, such as a payment, entered into the system's records. |
| timestamp/ˈtaɪmstæmp/ | A recorded date and time associated with an event or data item. |
| hash value/hæʃ ˈvæljuː/ | An output computed from input data by a hash function; distinct inputs can in principle produce the same output. |
Money without a bank
- Digital currency 数字货币 is money that exists only electronically.
- Its big challenge is trust — stopping the same money being spent twice.
- Blockchain 区块链 solves this with a tamper-evident shared record.
A shared, tamper-resistant digital ledger of transactions is called a ______.
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It underpins digital currencies.
Digital currency
- A digital currency exists only in electronic form — no coins or notes.
- It is stored and moved between people using computers, and can pay for things online.
- The problem: how do you stop someone spending the same money twice, or changing the records?
Each block stores the previous block's hash, chaining the blocks; changing one block breaks the chain.
Hashing behind a blockchain
A hash is one-way and a tiny change to the input flips much of the output — a blockchain chains these hashes so any tamper is obvious.
A digital currency is:
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Digital currency has no physical coins/notes; it is stored and moved by computers.
Blockchain
- A blockchain is a digital ledger 数字账本 — a shared record of every transaction 交易, copied across many computers, so no one person controls it and it is very hard to change.
- Transactions sit in blocks joined in a chain. Each block holds the data, a timestamp 时间戳, and a hash value 哈希值 (a code from its contents).
- Each block also stores the previous block's hash. Change an old block and its hash changes, so it no longer matches the next block — the chain breaks and the tampering is spotted at once.
A data centre full of servers: powerful computers that store websites and send them to you
A blockchain is:
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Being shared across many computers means no one controls it and it is hard to alter.
Match each blockchain idea to what it means.
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Blocks are chained by storing each other's hashes, so altering an old block breaks every link after it.
How does a blockchain reveal that an old block has been changed?
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Changing a block changes its hash; the next block's stored "previous hash" no longer matches, exposing the tampering.
The promise and the risk
- Digital currencies allow payments without a central bank, recorded on a blockchain.
- They offer fast global transfers but bring price swings and security risks.
You've got it
- digital currency = electronic-only money (no coins/notes)
- a blockchain is a shared digital ledger copied across many computers
- each block holds data + timestamp + hash, and the previous block's hash
- changing a block changes its hash → the chain breaks → tampering is detected