Hardware wallets explained: how they keep crypto safe

Hardware wallets explained: what the device actually does

With hardware wallets explained simply, the first surprise is that your coins are not stored on the device. Crypto such as Bitcoin exists as entries on a public blockchain. What you own is a private key: a very long secret number that proves you are allowed to move those coins. Whoever has the key controls the coins.

A wallet is anything that stores those keys. A phone app is a "hot" wallet, because the keys sit on a device that is connected to the internet. A hardware wallet is a "cold" wallet: a small, dedicated device built only to keep keys.

According to Trezor, a hardware wallet stores your private key offline and signs transactions inside the device. Only the signed transaction goes to your computer to be sent to the network. The key itself never leaves the device. That means even if your laptop is infected with malware, the attacker can't simply copy your keys.

You still check and approve each transaction on the device's own screen, with its own buttons. That matters: always confirm the amount and the receiving address on the hardware wallet, not only on your computer.

Seed phrases: the backup that matters most

When you set up a hardware wallet, it creates a recovery phrase, also called a seed phrase or secret recovery phrase. It is a list of ordinary words, usually between 12 and 24. Ledger describes it as "the backup of all the private keys stored in a given crypto wallet".

This is the most important thing to understand: the phrase is the wallet. If the device is lost, stolen or broken, you can type the phrase into a new device or another compatible wallet and get full access back. And anyone else who finds the phrase can do the same, without your device and without your PIN.

Most wallets follow a standard called BIP-39, which uses a fixed list of 2,048 English words. The phrase is simply a long random number translated into words that people can write down.

The maths makes the phrase practically impossible to guess. That shifts all the risk to how you handle it.

Buying a hardware wallet safely

Because a hardware wallet guards your keys, a tampered one could quietly hand them to someone else.

• Buy new, from the manufacturer. Trezor, for example, recommends its official store as "the best place to purchase" its devices, along with official resellers and its own Amazon storefront. It warns that buying from unauthorised third parties increases the risk of receiving a tampered device.
• Never buy second-hand, even sealed. You can't know what was done to it.
• Check the packaging for signs of tampering, as described in the manufacturer's instructions.
• Download software only from the manufacturer's official website. Fake versions of wallet apps exist and can look very convincing.

We don't compare or recommend specific models here. Check each manufacturer's own site for what its devices support.

Setting it up safely

1. Set it up yourself, from scratch. A new device should create a new recovery phrase for you. If a device arrives with a phrase already printed or filled in, don't use it.
2. Choose a PIN. On Trezor devices the PIN can be up to 50 digits, the wait doubles after each wrong attempt and the device wipes itself after 16 failed attempts, according to Trezor.
3. Write the phrase on paper, by hand, exactly, in order. A single wrong word gives you a different wallet.
4. Never photograph it, type it or store it in the cloud. Ledger advises keeping it offline and never entering it into a computer or phone.
5. Store it away from the device, somewhere safe from theft, fire and water. Some people use a metal backup plate.
6. Test with a small amount first. Send a small sum in, then send it out again, before moving anything larger.

Recovery: what happens when things go wrong

• Device lost or broken: buy a new one from the manufacturer and restore it with your phrase. Your coins were on the blockchain all along.
• PIN forgotten: after too many attempts the device wipes itself. Again, the phrase restores it.
• Phrase lost, device still working: move your crypto to a fresh wallet with a new phrase as soon as possible, while you still can.
• Phrase and device both lost: the crypto is gone. Trezor states it can't recover lost backups, and there is no bank or helpline that can.

Hardware wallet or exchange: pros and cons

An exchange may suit you if you hold a small amount, trade now and then, or would worry about looking after a phrase. Use only a provider authorised in your region; in the EU that means a crypto-asset service provider authorised under MiCA, which you can check in ESMA's register.

A hardware wallet may suit you if you hold an amount you couldn't stand to lose to a hacked or failed provider, plan to hold for a long time, and are confident you can store a phrase safely for years. It does not suit people who are likely to lose paperwork, or who don't want sole responsibility.

Common mistakes

• Storing the phrase as a photo or note on your phone. If your phone or cloud account is hacked, so is your crypto.
• Typing the phrase into a website that claims to "verify" or "sync" your wallet.
• Keeping the phrase in the same box as the device. One burglary takes both.
• Not telling anyone it exists. Think about how a trusted person could find out about it, without giving them the phrase today.

If you haven't bought any crypto yet, start with how to buy crypto safely, and if you're still deciding whether to, read what Bitcoin is first. For long-term money, most people build on low-cost ETFs instead.