What is a blockchain, in simple terms?
AnswerA shared record of data kept in a chain of linked blocks
A blockchain groups records into blocks, each linked to the one before it.
Tech · Facts & stats
Blockchain facts & stats
7 fact-checked facts about blockchain technology, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
What is a node in a blockchain network?
AnswerA computer that keeps a copy of the ledger and shares data
Nodes store and check the ledger and pass new data to other nodes.
Going deeper
What does a hash function produce?
AnswerA fixed-length fingerprint of data
Any input gives an output of the same length, and a tiny change gives a very different hash.
What does 'proof of work' require participants to do?
AnswerSpend computing effort solving a puzzle
Proof of work makes adding blocks costly in computation, which helps secure the chain.
What is a smart contract?
AnswerCode on a blockchain that runs automatically when conditions are met
Smart contracts carry out their programmed rules without a middleman.
Expert level
What data structure summarises all the records in a block with a single root hash?
AnswerA Merkle tree
A Merkle tree hashes pairs of items repeatedly until one root hash represents them all.
Which classic computer science problem about reaching agreement despite unreliable participants does blockchain consensus address?
AnswerThe Byzantine Generals Problem
It asks how parties can agree when some may be faulty or dishonest.
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