Collection 1 of 5 · 7 cards
Data & cryptography
Before blocks or networks, there are a few cryptographic tools. Hash functions turn data into fingerprints, key pairs let people sign without revealing secrets, and addresses are built from both. These seven cards cover the building blocks that every other collection relies on.
Cards in this collection
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What is a hash function?
A hash function is a calculation that turns data of any size into a short string of fixed length — a digital fingerprint that changes completely if even one bit of the input changes.
2 min read
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What is SHA-256?
SHA-256 is a specific, standardised hash function from the SHA-2 family that turns any input into a 256-bit fingerprint, and it is the hash function at the heart of Bitcoin.
2 min read
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What is a Merkle tree?
A Merkle tree is a way of hashing many items in pairs, level by level, until a single hash — the Merkle root — stands for all of them at once.
2 min read
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What is a public key?
A public key is the shareable half of a key pair: a value calculated from a private key that lets anyone check signatures made with that private key, without being able to make them.
2 min read
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What is a private key?
A private key is a secret number that lets its holder create digital signatures — and on a blockchain, whoever can sign for an address controls whatever is recorded to it.
2 min read
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What is a digital signature?
A digital signature is a short piece of data, made with a private key, that proves the key holder approved one specific message and that the message has not been altered since.
2 min read
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What is a blockchain address?
A blockchain address is a short public identifier, usually derived from a public key by hashing, that tells the network where units or tokens are recorded.
2 min read