What is a multisig vault?

A simple introduction to Casa vaults, keys, and how multisig protects your Bitcoin and Ethereum.

What is the problem with a single key?

Most cryptocurrency wallets work with a single private key. That key manages everything meaning whoever has it controls the funds. If it's lost, stolen, or destroyed, the funds are gone. Forever.

This is often referred to as a "single point of failure." One mistake, one accident, one bad actor can be the complete loss of your Bitcoin or Ethereum.

What is a Casa vault?

A Casa vault is a multisig wallet, short for "multi-signature." Instead of using one key, your vault uses multiple keys. And to send a transaction, more than one of them must approve it.

Think of it like a bank vault that requires two people to turn their keys at the same time. No single key can open it alone therefore making it much more difficult for others to gain access.

How does a 3-key vault work?

Your 3-key vault has three keys:

• Mobile key This key lives securely on your phone, inside the device's secure enclave (a dedicated chip that keeps sensitive data isolated). You'll use this key most often when signing transactions.

• Hardware key This key lives on a physical hardware device, like a Trezor or Ledger, that you keep offline. Because it's separate from your phone and separate from the internet, it's much harder for an attacker to reach.

• Casa Recovery Key Casa holds this key on your behalf. It exists as a backup for emergencies.  If you lose your hardware device for example. Importantly, Casa cannot use this key alone to move your funds. It only becomes useful in combination with one of your other keys, and only with your authentication.

Why 2-of-3?

Your 3-key vault requires any 2 of those 3 keys to send a transaction. This is what "2-of-3 multisig" means.

This design means:

• Losing one key doesn't mean losing your funds. If your phone is lost or stolen, you still have your hardware key and your Casa Recovery Key. Your funds are safe.
• No single key is enough for an attacker. Someone who gets hold of your hardware device still can't move your funds without a second key.
• Casa cannot access your funds unilaterally. Even though Casa holds the Recovery Key, it requires your authentication and your own key signatures to complete any transaction.

Is Casa a custodian?

No. Casa only holds one key, the Recovery Key.  That key alone cannot move your funds. You are always in control. This is what distinguishes Casa from an exchange or a custodial wallet, where the company holds all the keys and you are trusting them to safeguard your funds on your behalf.

With Casa, the bitcoin or ethereum in your vault is yours. The vault is yours. Casa's role is to help you secure it.

What you'll need to get started

Before setting up your 3-key vault, you'll need:

• An email address to create a Casa account
• The Casa app downloaded on your iPhone or Android device
• A compatible hardware device — Casa supports Trezor, Ledger, Coldcard, Keystone, Passport, and YubiKey
• A computer to connect your hardware device during the setup process

Not sure which hardware device to choose? Choosing a Hardware Device for Your Casa Vault

Ready to set up your vault? Getting Started with the 3-Key Vault