Learn · Blockchain

Blockchain, chapter by chapter.

Start with a digital fingerprint, then build towards wallets and shared control. Open any chapter below, or follow them in order.

8 interactive chapters. Each chapter includes an experiment you can try in your browser.

1. Chapter 1 · Start here

   What is a hash?

   Type anything, watch its fingerprint change. Crack a PIN by brute force, watch a birthday-attack collision land, then mine your own block. Hashing is the atom of blockchain: start here.

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2. Chapter 2

   Blocks & chains

   Build a block, break a blockchain, then repair it by re-mining. One edit invalidates all of history after it. See why, hands-on.

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3. Chapter 3

   Consensus & proof of work

   Explore an attacker’s catch-up race and see how hashpower and the starting deficit affect this simplified model.

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4. Chapter 4

   Wallets, keys & signatures

   Generate a real key, sign a real message, verify it, then lose the key and feel exactly what 'not your keys' means.

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5. Chapter 5

   Mnemonics & seed phrases

   Real BIP39: turn coin flips into 24 words, sabotage the checksum, derive the seed, and learn where the words should live.

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6. Chapter 6

   Hot & cold wallets

   Slide across the storage spectrum, fall for a blind-signing trap, then explore a simulated air-gapped signing ceremony in your browser.

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7. Chapter 7

   Multisig: many keys, one vault

   Explore a simulated 2-of-3 vault, collect signatures to a threshold, then lose keys on purpose. Bitcoin multisig vs Gnosis Safe, compared.

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8. Chapter 8

   MPC: signing without reassembly

   Split a secret with real Shamir sharing, see why splitting isn’t signing, then explore threshold signing without reassembling a key. The custody season finale.

   Open chapter 8 →