Toly’s coat had two pockets. In the outside one was a card with a long string of letters and numbers on it. That was his address. He could pin it to any noticeboard in town, and people used it to send him things, the same way you’d use a house address to send someone a letter.

The inside pocket was different. It buttoned shut, it had a tiny lock, and Tick had volunteered to guard it. Inside was his private key, and folded up very small, the recovery phrase that could rebuild it. Anyone holding those could spend whatever the address had.

On Solana an address is usually a public key, and the wallet holds the private key that goes with it. Together they’re called a keypair. When you send SOL or use an app, the wallet uses the private key to make a signature, a kind of mathematical seal on that exact transaction. Validators check the seal using only the public key. The private key never leaves the pocket.

The clever bit is that anyone can check a seal is real, but nobody can make a new one without the private key. And if you change a single detail of the transaction, the old seal stops fitting.

Halfway down the high street a fox in a very official hat stepped out. “Wallet inspection,” it said. “I’ll just need your recovery phrase.” Tick ticked so loudly the fox’s hat fell off, and Toly kept walking. Nobody genuine will ever ask for your recovery phrase or private key. Not a help desk, not an app, and definitely not a fox in a hat.

Before Toly could leave town, Pim made him take a quiz. Pim makes everybody take a quiz. Yes, reader, that includes you.

Sort each thing into the right pocket. The outside pocket is for things that are safe to share, and the inside pocket is for things you must never give away. After each answer, the book explains why.

Toly got full marks, mostly because Tick kept glaring at the wrong pocket. Then, with his address pinned to his hat, he followed the sound of a brass band towards the market. Something over there smelled of popcorn, fresh paint and very dodgy business plans.