Creating a watch-only bitcoin wallet in Specter

Specter Desktop is fully open source and has some of the best support for bitcoin hardware devices. We also like that you never need to load your private keys into Specter. Specter is also backed by your own personal full node.

The following guide explains how to create a watch-only wallet in Specter using the public keys available to you in your Casa app. 

Or learn more about the Casa app here. 

🚨 Important Note: Specter Desktop requires you to be running a full node, which is more resource-intensive than Electrum. On the other hand, it provides you with a stronger privacy model.

While Specter will display your unused derived "future" addresses, you should only deposit funds to either the current address that the Casa app is showing you, or previous addresses that you have deposited to in Casa App. "Skipping" addresses in your vault and depositing to later derived addresses may cause the deposit to not appear in the Casa app. This is due to what's known as the "gap limit" issue where some wallets, ours included, do not automatically scan past unused addresses to determine a user's balance or transaction history. If this happens, you must make deposits of any amount to the empty addresses within the "gap." 

See Mind the bitcoin address gap for more details on the gap limit.

What you'll need:

1. Laptop or desktop that can run Specter Desktop. We like Ubuntu or PureOS, but Mac and Windows work just fine. You'll need at least 300GB of disk space for the full node.
2. Android or iOS device running the Casa app
3. (Optional) Encrypted messaging app running on both devices. We like Keybase or Signal

🛎️ A note for non-Casa customers: This process will work with any multisig account. Just collect the public keys from your wallet provider.

1: Export public keys

To set up your watch-only wallet, you will need to get the extended public key for each one of your signing devices.

1. Open the Casa app
2. Select the multisig account from the top navigation (Your 3-key or 5-key vault)
3. Tap the icon for the Casa Recovery Key
4. Tap "View Public Keys"
5. Choose "BTC Account"
6. Tap the Ypub to copy the key
7. Save it locally, or send it to yourself using an encrypted messenger
8. If applicable, repeat steps 3-7 for every other device in the keyset

Once you've gathered the public keys, transfer the data to the computer where you’re setting up the watch-only wallet. Encrypted messaging services are a great option, or you can physically transfer the data via a USB drive. We do NOT recommend emailing the keys to yourself, since you risk exposing your account’s addresses to eavesdroppers.

2. Download and install Specter Desktop

1. Install Bitcoin Core
2. Generate rpcauth for your node with this script
3. Recommended bitcoin.conf for Bitcoin Core:

   blockfilterindex=1
   
   rpcauth=<YOUR_RPC_CREDS>
   
   server=1

4. Install Specter Desktop and make sure it can talk to Bitcoin Core. We recommend this guide.

3. Create your devices

For each of your keys:

1. Click "Add Device"
2. Select "Other Device"
3. Enter a name for the device.
4. Click "Edit"
5. Delete any pre-filled derivation paths.
6. Click "Paste xpub"
7. Paste in the extended public key you copied from the Casa app
8. Derivation path should auto fill in "m/"
9. Click "Add Device"

4. Create your watch-only wallet

1. Click "Add new wallet"
2. Click "Create multisignature wallet"
3. Select all of the devices
4. Click "continue"
5. Name the wallet
6. Highlight "Nested Segwit"
7. Ensure that the number after "Using" matches the number of signatures required to transact
8. Check "scan for existing funds"
9. Click "create wallet"

If everything went well, you’ll see a new wallet with a "rescanning blockchain" progress percentage. If the blockchain scanning completes and does not find your funds, then you likely entered the wrong public key or derivation path somewhere during the process.

5. Verify receive addresses

Now that you have your watch-only account active, let’s verify your next receive address:

1. Open the Casa app
2. Tap your vault to select the appropriate account
3. Tap "Deposit funds" to request to generate the next address
4. In Specter, click your wallet on the left and then click the "Receive" tab at the top of the screen
5. The address displayed should match the one in your Casa app
6. If it doesn’t match, tap "Get new address" in Specter and check that address instead
7. If you still do not see your Casa receive address, click "Show past addresses"

For any questions about watch-only wallets, or anything else related to your security, please reach out to us here.