Blockchain: why link blocks?
What you will learn
Draw three blocks with links to their predecessors. Explain what needs checking if the first block changes.
A blockchain is a digital log of records grouped into blocks linked by cryptographic fingerprints.
On a network such as Bitcoin, many computers check the ledger under shared rules. Each block refers to its predecessor’s fingerprint, called a hash. Changing a record changes its hash and reveals a mismatch in the links that follow. Hashing is not encryption that hides information. Links alone do not prevent forgery: transaction validation and consensus also protect the history. Well-confirmed history is difficult to alter, but protection is not absolute.
Imagine a shared class notebook: each page includes the previous page’s fingerprint. A later edit creates a mismatch. This is an analogy; computers use cryptographic calculations.
Draw three blocks with links to their predecessors. Explain what needs checking if the first block changes.
Bitcoin · White paper ↗Check your understanding
What does the cryptographic link to the previous block do?
- Hide the coin’s price
- Link records and reveal changes
- Guarantee a profit
Answer and explanation
Link records and reveal changes. The link helps detect changes to history; it does not promise returns.
Does hashing alone protect the whole network?
- No, validation and consensus rules are also needed
- Yes, transactions need no checking
- Yes, it prevents every attack
Answer and explanation
No, validation and consensus rules are also needed. Protection depends on several mechanisms working together.
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