Digital currency and blockchain
| English | Chinese | Pinyin |
|---|---|---|
| digital currency | 数字货币 | shù zì huò bì |
| blockchain | 区块链 | qū kuài liàn |
| digital ledger | 数字账本 | shù zì zhàng běn |
| transaction | 交易 | jiāo yì |
| timestamp | 时间戳 | shí jiān chuō |
| hash value | 哈希值 | hā xī zhí |
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 ______.
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:
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:
Being shared across many computers means no one controls it and it is hard to alter.
Match each blockchain idea to what it means.
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?
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