The mobile key in the Casa app makes storing a key on your mobile device (and backing it up) simple, safe, and easy.
The mobile key is one of the keys in your vault that can be used to sign and send transactions.
The mobile key is standard in the 3-key vault, and is also used as a key in the 5-key vault.
We do have the option to replace the mobile key with a second hardware key in the 3-key vault if desired (for advanced users only!). Please note that replacing the mobile key with a second hardware key is available for BTC vaults only.
How is it generated?
The mobile key is generated locally on your personal mobile device in its Secure Enclave. The key never touches Casa servers. This is why even if someone obtained access to your Casa account credentials, they would not be able to access your mobile key on their own device unless they also obtained access to the key's cloud backup.
How is it backed up?
The mobile key is encrypted and backed up to your phone's default cloud service. No need to write down a seed phrase!
If you're using an iPhone, the mobile key is backed up to iCloud. If you're using an Android phone, the mobile key is backed up to Google Drive.
In order for the mobile key to be backed up automatically, you need to be signed into your Apple (if you're using an iPhone) or Google (if you're using an Android phone) account in the system settings of your phone.
At no point does Casa ever have access to your mobile key, and since the backup is encrypted, your cloud storage provider can't access your key either.
What if I get a new phone?
Because the key only exists on your specific phone and backed up to your cloud drive, if you get a new phone, you need to make sure you get a copy of the key on the new phone. To do this, simply log into the Casa app on your new phone, and restore the key from backup by performing a health check. As long as you're signed into the same Apple or Google account on the new phone as when you first set up the key, the Casa app will find the backup automatically!
If you would like to have an additional way to backup your mobile key, you can do so by saving an offline QR code by following the instructions here:
QR Code Backups for the Mobile Key and Pay Key
If you ever lose your phone or get a new phone, we have guides on how to restore the Casa app on a new phone. See:
Transitioning to a new Android phone
If you're transitioning between phone operating systems, make sure you get the key set up on the new phone before you get rid of the old one! See the instructions in our article Switching between iPhone and Android for more details.
How do I set it up?
To set up your mobile key, simply tap "Connect" on your vault, then choose "Set Up Mobile Key."
Once your vault is set up, the mobile key can immediately be used for signing transactions in the Casa app. Periodically (at least twice per year, or once every six months), we recommend doing a quick health check on the mobile key to make sure it's on your device and correctly backed up to the cloud.
Learn more about health checks.