What is a seed phrase?

TL;DR: A seed phrase is a list of 12 or 24 words that acts as a backup of a hardware device's private key (the secret information used to authorise transactions). Anyone who has the seed phrase can recreate the key and spend the bitcoin it controls, so it must be kept private and stored offline. In a Casa multisig vault (a vault requiring more than one key to authorise a transaction), no single seed phrase can move your vault balance on its own. Recording a seed phrase is also optional, because a lost device can be replaced using your remaining keys through a key rotation (replacing one key in the vault with a new one).

What a seed phrase is

When you set up a hardware device, the device generates a private key, which is the secret information that authorises spending from a bitcoin address. A seed phrase is a human-readable backup of that private key, presented as a list of 12 or 24 simple English words shown on the device's screen during setup.

Those words are not random in the everyday sense. They come from a standardised list of 2,048 words, and the specific words in a specific order encode the private key itself. This means:

If you have the seed phrase, you have the key. Entering the words into any compatible hardware device recreates the exact same key, even if the original device is lost, broken, or destroyed.

If someone else has the seed phrase, they also have the key. A seed phrase written down, photographed, or typed into a computer can be used by anyone who finds it. The seed phrase is the key, in word form.

What a seed phrase is not

A seed phrase is sometimes confused with other pieces of security information. It is not:

A password. Passwords can be reset. A seed phrase cannot. There is no “forgot my seed phrase” option, because no company, including Casa, has a copy.

A PIN. Your hardware device's PIN protects the physical device from being used by someone who picks it up. The seed phrase protects the key itself, independently of any device.

Something Casa stores for you. Casa is non-custodial, meaning your bitcoin is secured by your own keys. Casa never sees, stores, or asks for your seed phrases, and Casa cannot access your vault balance.

Seed phrases in a Casa multisig vault

With a single hardware device holding a single key, the seed phrase is the only safety net. Lose the device and the seed phrase, and the bitcoin is unrecoverable. This is why seed phrase storage is such a heavy responsibility in single-key setups.

A Casa vault works differently. Your vault uses multiple keys, and more than one key is required to authorise any transaction. This changes the role of the seed phrase in two important ways:

1. No single seed phrase can move your funds. Even if one seed phrase were lost or stolen, an attacker could not spend from your vault with it alone. They would still need additional keys to meet the vault's signing requirement.

2. Recording a seed phrase is optional. If a hardware device is lost or stops working, you can replace that key using your remaining keys by performing a key rotation. Because the vault itself provides the recovery path, many members choose not to record seed phrases at all. This removes the risk of a written seed phrase being found by someone else.

If you choose to record a seed phrase: write it on paper or stamp it in metal, store it somewhere secure such as a safe or safe deposit box, and never photograph it, type it into a computer or phone, or store it in cloud storage. If you choose not to record one: simply skip or dismiss the seed phrase backup step during device setup where the device allows it, and rely on key rotation as your recovery path.

Keeping your seed phrase safe

If you do keep seed phrases, follow these practices:

Keep it offline. Never enter a seed phrase into a website, app, or computer unless you are deliberately recovering a key onto a new hardware device.

Never share it. No legitimate company will ever ask for your seed phrase. Not Casa, not a hardware device manufacturer, not “support.” Anyone asking for your seed phrase is attempting to steal your bitcoin.

Need help?

If you have questions about seed phrases or how recovery works in your vault:

Standard and Standard Plus members: email help@team.casa.
Premium, Private Client, and Business members: reach out to your Casa advisor or schedule a call through the Casa app.