Wallets & Keys 101

A crypto wallet does not hold your coins. The coins are entries on a public ledger, and they never leave it. What the wallet holds is the private key — the secret that authorises moving those entries.

That distinction sounds pedantic and it explains almost everything else on this page: why restoring a phrase on a new phone brings everything back, why losing a key loses the funds even though you can still see them on the ledger, and why nobody can help you afterwards.

Keys, in one paragraph

Every address has a pair: a public key, which anyone can see and from which the address is derived, and a private key, which only you have. Spending signs a transaction with the private key; anyone can verify the signature against the public key without ever learning the private one. That one-way relationship is the whole of crypto ownership. Bitcoin Encryption covers the cryptography properly.

Custodial or self-custody: the actual decision

Every wallet is one or the other, and the difference is simply who holds the key.

“Not your keys, not your coins” is the slogan, and it is accurate: a balance on an exchange is a claim on that company, not property you hold. It is also incomplete advice. Self-custody moves the risk rather than removing it — from a company that might fail to you, who might lose a piece of paper. For a beginner holding a small amount, a reputable exchange is often the safer of the two. The mistake is not choosing custodial; it is not knowing which one you chose.

Seed phrases

Most wallets show you twelve or twenty-four ordinary words when you set them up. That is your seed phrase, and it encodes every private key the wallet will ever generate. Anyone with those words has the funds — on any device, in any country, forever. It is not a password protecting an account somewhere; it is the account.

Which produces a short, unglamorous set of rules:

• Write it on paper. Not a screenshot, not a notes app, not an email to yourself, not cloud storage. Anything that syncs is one breach away from being public.
• Store it where fire and water are not a single point of failure. Two locations beats one clever hiding place.
• Nobody will ever legitimately ask for it. Not support, not a wallet developer, not a “migration” or “validation” page. Every single request is theft. There are no exceptions to hedge against here.
• Test the recovery before you rely on it. Restore onto a spare device while the amount is small. A phrase you have never tested is a plan you have never tested.

Hot, cold, and when hardware is worth it

A hot wallet lives on an internet-connected device — a phone app or a browser extension. Convenient for spending, permanently exposed to whatever reaches that device. A cold wallet keeps keys on something that never touches the internet, usually a small dedicated device that signs transactions internally and only ever hands back the signature.

The point of hardware is not that it is unbreakable. It is that malware on your laptop cannot reach a key that was never on the laptop. The sensible arrangement for most people is both: a hot wallet with what you would carry in a physical wallet, cold storage for the rest.

Buy hardware from the manufacturer directly. A device bought second-hand or from a marketplace reseller may arrive pre-initialised with someone else's seed phrase — and any device that comes with a phrase already written down is a trap, without exception. A genuine device generates its phrase in front of you, on first setup.

How people actually lose funds

Not by having encryption broken. Almost always by one of these, in roughly this order:

• Losing the phrase. Never written down, written down and lost, or stored on a device that died. Undramatic and irreversible.
• Giving the phrase away. To fake support, a fake wallet app, or a page that looked like the real one. The theft is instant and complete.
• Signing something they did not read. Approving a contract permission that lets an address move tokens on your behalf, then finding out what that meant later. This is the modern version, and it does not require your seed phrase at all.
• Sending to the wrong address or network. Transactions are final and there is no recall. Check the first and last characters, and send a small test first when the amount matters.
• Leaving everything on an exchange that failed. Rarer than it was, and it has happened repeatedly to large platforms people considered safe.

Four of those five are procedural, not technical. How to spot a crypto scam covers the ones with a person on the other end.

A workable setup

No hardware is required to start, and pretending otherwise puts people off doing anything sensible at all. A reasonable progression: keep small amounts on a reputable exchange while you are learning; move to a self-custody hot wallet once you understand seed phrases and have tested a recovery; add hardware when the amount would genuinely hurt to lose. Review it when the number changes — most losses happen to setups that were appropriate for a much smaller balance.