How to use 2/2 PSBT Multi-signature with Cobo Vault, Coldcard and Specter

Preperation:

1. Cobo Vault Essential or Pro upgraded to firmware version v1.4.1(BTC-only). Create recovery phrase A.

2. Coldcard upgraded to firmware version v2.1.0 or later. Create recovery phrase B.

3. Specter (v0.7.0 or later) installed.

4. MicroSD card（≤32GB；default FAT32 format）

Add device on Specter

- Add Cobo Vault on Specter

1. Click [+ Add new device] on Specter. Enter the name and select Device Type.

2. You can choose using QR code or import .json file to get the xpubs of recovery phrase A imported to Cobo Vault.

*Tips: If you want to switch to [Test Net], please go to Cobo Vault > Settings > Blockchain > Test Net. Then continue with the following steps.

1) QR code

① Cobo Vault > Menu > Multisig Wallet > press [•••] icon on the top right > Show/ Export XPUB

② Specter > Scan > scan the QR code show on Cobo Vault

2) File

① Insert microSD card into Cobo Vault > Menu > Multisig Wallet > Show/ Export XPUB > Export All > Export

② Insert micro SD card into PC/Mac > Specter > Choose files > select and open the .json file exported from Cobo Vault

3. Click [Continue], add Cobo Vault successfully.

- Add Coldcard on Specter

1. Click [+ Add new device] on specter. Enter the name and select Device Type.

2. Insert microSD card into ColdCard > Settings > Multisig Wallets > Export XPUB > Get xpubs of recovery phrase B from ColdCard

3. Insert micro SD card into PC/Mac > Specter > Choose files > select and open the .json file exported from ColdCard

4. Click [Continue], add ColdCard successfully.

Create watch-only wallet for 2/2 PSBT multisig wallet on Specter

1. Specter > Add new wallet > Multisignature wallet

2. Set the name, Type, number of cosigners and number of needed signatures. Pick the devices you want to use as cosigners. (You need to add them as new devices.) Click [Continue].

3. Click [Create wallet], create watch-only wallet for 2/2 PSBT multisig wallet successfully.

Create 2/2 PSBT multisig wallet on Coldcard

1. Insert the microSD card into Coldcard with .json file exported from Cobo Vault in the card.

2. Settings > Multisig Wallets > Create Airgapped

3. Set address type(Default-P2WSH) and the number of cosigner(2 of 2)

4. Confirm(√) and complete creating a 2/2 multisig wallet

5. You will get a file named “export-CC-2-of-2.txt” on your microSD card after the previous step. You will need it to import multisig wallet to Cobo Vault.

Tips: If you didn’t get the file, please export manually by following instructions:

1. Insert the microSD card into Coldcard

2. Settings > Multisig Wallets > 2/2: CC-2-of-2 > Coldcard Export > “export-CC-2-of-2.txt”

Import 2/2 PSBT multisig wallet to Cobo Vault

1. Insert the microSD card into Cobo Vault with “export-CC-2-of-2.txt” file exported from Coldcard in the card.

2. Menu > Multisig Wallet > Import Multisig Wallet

3. Select file “export-CC-2-of-2.txt” > Confirm

Send a 2/2 PSBT multisig transaction

- Create unsigned transaction on Specter

1. Specter > Multisig Wallet > Send > Input the recipient address and amount > Create unsigned transaction

- Sign with Cobo Vault

1. Specter > Cobo Vault > Sign with QR codes

2. Cobo Vault > press the [Scan] icon > scan the QR code show on Specter interface > Sign > Password verification

Tips: If you have difficulty on QR code scanning, please tap the QR code to adjust the density of the QR code and retry.

3. Specter > Scan signed transaction > scan the QR code show on Cobo Vault > Cobo Vault signed successfully

Tips: You can also sign transactions with the SD Card file.

1. Specter > Cobo Vault > Sign with SD Card file > Download transaction (save the unsigned transaction file to microSD card)

2. Insert the microSD card into Cobo Vault > press the [microSD card] icon > select and open the unsigned transaction file > Sign > Password verification > press [touch here] to export partially signed transaction file to microSD card

3. Insert the microSD card into PC/Mac > Specter > Upload signed transaction > Select and open the partially signed transaction file exported from Cobo Vault > Cobo Vault signed successfully

- Sign with Coldcard

1. Insert the microSD card into PC/Mac > Specter > ColdCard > Sign with SD card file > Download transaction (save the unsigned transaction file to microSD card)

2. Insert the microSD card into Coldcard > Ready To Sign > OK > export partially signed transaction file to microSD card

3. Insert the microSD card into PC/Mac > Specter > Upload signed transaction > Select and open the partially signed transaction file exported from ColdCard > ColdCard signed successfully