The school / Lesson 01 of 03
What a blockchain records
A record shared across computers
A blockchain groups records into blocks. Each block refers to a previous block using a cryptographic hash. A hash is a short result calculated from data; changing the data changes the result. The links make alterations detectable, but they do not establish whether a claim entered into the system was true.
Nodes check the rules
Nodes are computers running software that checks records against a protocol. A network also needs a way to agree which valid history to follow. Different networks use different mechanisms. Reading that a project uses a blockchain does not tell you which rules it uses or who can change them.
The network and the application
An application can use a public network while keeping parts of its service elsewhere. A website, database and support system can have their own operators and failure points. Ask which part of a claim is recorded on the network and which part depends on an outside service.
A question to take into the news
When an article announces an upgrade, find out whether it describes a proposal, a test environment or a change on the main network. Those are different stages. The Platåberget brief in this edition is a useful place to practise that distinction.
Check your understanding
Does a record on a blockchain prove that the original statement was true?
Read the answer
No. It can provide evidence about the record and its history. The truth of an outside claim still needs evidence.
Further reading: Ethereum documentation.
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