// learn · episode 04 · season finale
Wallets, keys & signatures
Episode 3 showed how a network agrees on history. Here we explore how keys authorize actions: generate a P-256 keypair, sign a message, and verify its signature locally. Bitcoin and Ethereum use different key and address conventions. The identifier below is for this demonstration; no wallet is deployed and no assets move.
01 · the key
Your key is just a number
This demo needs no account. It generates a private key using secure browser randomness. With a correctly generated key, the chance of another person independently choosing the same value is negligible. The key provides signing capability, not proof of legal ownership.
your private key — 256 bits, freshly generated
generating…
how big is 2²⁵⁶?
About 1.2 × 10⁷⁷ possible keys — within shouting distance of the ~10⁸⁰ atoms in the observable universe. Exhaustive guessing is impractical with current computing. Secure randomness, implementation, and key handling are also essential.
About this demo
This educational key is generated and used locally in your browser. Do not use it for real funds. A private key enables signatures; possession alone does not establish legal ownership.
02 · the pipeline
Key → public key → demo identifier
A private key produces a public key. This demo then hashes the public key to make an illustrative identifier. Recovering a securely generated private key from its public key is computationally impractical with known classical methods; different blockchains encode addresses in different ways.
private key — SECRET
generating…
public key — shareable
…
demo identifier — not an on-chain address
…
This educational pipeline uses P-256, then SHA-256 of the public key, retaining the last 20 bytes. It does not produce a Bitcoin or Ethereum address. Real networks specify their own key formats, hash functions, address types, and encodings. Do not send assets to this identifier.
03 · signing authority
Sign & verify
A signature lets someone check that a message was signed with the corresponding private key, without seeing that key. You’re about to make and verify a real signature over a demonstration message.
This is the whole trick of ownership: the private key stays secret, yet anyone can check your claim using only the public key. When a wallet app "sends crypto", this is all it really does — sign a message saying so, and broadcast it for the miners of episode 3 to bury under confirmations.
04 · the hard truth
What happens when a key is lost
This demonstration has one private key and no recovery mechanism. Remove the key and you can no longer create signatures with it. Real arrangements depend on their backups, recovery procedures, and signing policy. Try the local simulation below.
private key
∅ gone. not misplaced — gone.
the sober numbers
Losing access to a key can prevent spending when no recovery path exists. Many wallets use a seed phrase to derive a seed from which keys can be recreated. Protect any passphrase and the relevant wallet information too. But that only moves the question: where do those words live, and who can find them when you're gone? That's not a technology problem. It's an inheritance problem.
season complete
Four building blocks, explored
Hashes, linked blocks, consensus rules, and signatures work together to make records inspectable and actions verifiable. Their guarantees depend on the algorithms, implementation, and operating assumptions. These demonstrations introduce the mechanisms without reproducing a complete blockchain.
One thread runs through this whole series: keys don't survive their owners by default. Digital assets that outlive their owners need a succession plan.
That's the problem I work on →