Your crypto wallet and seed phrase, in plain words

Your phone slips into a lake, and your crypto wallet app goes down with it. Are your tokens gone? If twelve words are written on a piece of paper at home, no. If they are not, there is nobody to call.

Everything else about wallets follows from that difference, so it is worth seeing how it works.

The mailbox and the key

Tokens are balances on a blockchain, the shared record of who owns what. They do not sit inside your phone. The wallet app holds something else: a key that can move them.

Picture a mailbox standing on the chain. Your address is the slot. It is a long string of letters and numbers, and you can hand it out freely. Anyone can drop tokens through it, like 50 USDC on Base. (USDC is a digital dollar, and Base is one of many chains.) Knowing where the slot is does not let anyone reach inside.

The key is what opens the box. When you send something out, your wallet signs with that key, a little like signing a check. Signing proves the instruction came from whoever holds the key, and the chain then carries it out. An app you have given permission can move tokens later, but only because your key signed that permission first.

The key, written as words

When you set up a new wallet, it usually gives you twelve words, or sometimes twenty-four. That is your seed phrase. It is your key in a form a person can write down. Type those words into a wallet app on any phone and the same key is rebuilt, along with your way into the same mailbox.

Two short stories show both sides of this.

Sara loses her phone. She buys a new one, installs a wallet app, picks the option to restore a wallet and types her twelve words. Her 50 USDC on Base is right there. It stayed on the chain the whole time.

Now say someone photographs Sara's paper. They type the words on their own phone and hold the same key. When they send her tokens out, the chain sees a properly signed instruction and carries it out. It cannot tell who is holding the key. Whoever has the words has the wallet.

Keeping the words

• Write them on paper, in order, and check the spelling.
• Keep that paper somewhere only you can reach.
• Do not photograph them, or save them in a notes app or an email.
• Type them only into a genuine wallet app, and only when you are restoring a wallet.
• Keep them from everyone. A real helper has no reason to ask, whatever name or logo they show.

What people get wrong

"My app password protects me." A PIN or password only locks the app on that one phone. Anyone with the words can skip it by using their own phone.

"Deleting the app deletes my tokens." It does not. The tokens stay on the chain, and the words bring your access back.

"Someone can reset it for me." There is no reset button to press. If the phone and the words are both lost, your access goes with them.

That last one is the real trade. Keeping your own key like this is called self-custody. If a company holds tokens for you, it holds the key and can offer a password reset. With self-custody, nobody else can move your tokens unless your key allowed it, and nobody else can rescue them either.

In short

• A wallet holds a key, and your tokens stay on the blockchain.
• Your address is the slot: anyone can send to it, and only the key opens it.
• The seed phrase is that key in words, so whoever has the words has the wallet.
• Keep the words on paper and show them to no one, because there is no reset.

More one-minute DeFi explainers: cleave.fi/blog