Electrum 2/2 PSBT Multi-sig

Keystone firmware version V1.1.1 (BTC-Only) or newer supports PSBT Muti-signature function. This instruction will show how to create a 2/2 PSBT Multi-signature with Keystone, Coldcard and Electrum V4.1.2 in details.

2/2 PSBT Multi-sig is not a good quorum. This tutorial is just for the purpose of showing how to use Keystone and Coldcard to set up your multi-sig wallet with Electrum. Learn more about picking a good quorum: https://btcguide.github.io/quorum

I. Preparation

1. Firmware version V1.1.1 (BTC-Only) or newer running on Keystone Essential or Pro.

(Please read How to upgrade firmware for more details.)

2. Coldcard upgraded to firmware version V2.1.0 or newer.

3. MicroSD card (≤512GB; Default FAT32 format).

How to Format a MicroSD Card to FAT32?

4. Electrum Wallet (V4.1.2 or newer) running on PC/Mac.

Tips: If you want to switch to [Test Net], please go to "Keystone > Settings > Blockchain > Test Net" and "Coldcard > Settings > Blockchain > Test Net". Then continue with the following steps.

II. Create a 2/2 multisig wallet with Keystone and Coldcard

- Create multisig wallet on Coldcard

1. Export Keystone's Xpub to a MicroSD card

1) Insert the MicroSD card into Keystone

2) Touch [Menu] > [Multisig Wallet] > Press the [•••] button on the top right > [Show/Export XPUB].

3) Touch [Export All] > [Export].

2. Create multisig wallet on Coldcard

1) Take the MicroSD card from your Keystone and insert it into Coldcard.

2) [Settings] > [Multisig Wallets] > [Create Airgapped]

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

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

3. After the previous steps, you will get 2 files on your microSD card:

1) “export-CC-2-of-2.txt” - this is for importing multi-sig wallet to Keystone - allows Keystone to check the genuinity of multisig when signing.

2) “el-CC-2-of-2.json” - this is for creating watch-only wallet on Electrum.

If you didn’t get these two files, please export manually by following the instructions:

1) Export the multisig wallet file (for importing multisig wallet to Keystone) to the microSD card.

① Insert the microSD card into Coldcard.

② [Settings] > [Multisig Wallets] > [2/2: CC-2-of-2] > [Coldcard Export] > Export the “export-CC-2-of-2.txt” file to the microSD card.

2) Export the multisig wallet file (for creating a watch-only wallet on Electrum) to the microSD card.

① Insert the microSD card into Coldcard.

② [Settings] > [Multisig Wallets] > [2/2: CC-2-of-2] > [Electrum Export] > Export the “el-CC-2-of-2.json” file to the microSD card.

- Import multisig wallet file to Keystone

1. Take out the microSD card from Coldcard and insert it into Keystone.

2. Tap [Menu] > [Multisig Wallets] > [Import Multisig Wallet].

3. Select file “export-CC-2-of-2.txt” > Click on [Confirm].

- Import multisig wallet file to Electrum and create watch-only wallet

1. Take out the microSD card from Keystone and insert it into PC/Mac.

2. Run Electrum, then click on [choose...] > Select file “el-CC-2-of-2.json” > [Open] > [Next]> [No].

Note: As Electrum doesn’t have a Keystone plugin (we are working on that), Keystone can’t generate an Electrum skeleton json file. So you have to export the Electrum skeleton json file from Coldcard to set up the watch-only wallet on Electrum.

IV. Sending bitcoin from the 2/2 multisig address (Keystone & Coldcard)

- Generate multisig transaction on watch-only wallet(Electrum) and export unsigned multisig transaction file to MicroSD card.

1. Click on [Send] > Enter destination address and amount > [Pay] > [Send].

2. Click on [Export] > [For hardware device; include xpubs] > [Export for file] > [Save].

- Partially sign multisig transactions on Coldcard

1. Take out the microSD card from PC/Mac and insert it into Coldcard.

2. [Ready To Sign] > Select transaction file.

3. Confirm and export partially signed multisig transaction file to microSD card.

- Complete sign multisig transaction on Keystone

1. Take out the microSD card from Coldcard and insert it into Keystone.

2. Enter Multisig Wallet > Press "MicroSD card" icon on the top right > Select the partially signed transaction file > Confirm transaction details and press [Sign].

3. Password Verification > Press [Export] to export a fully signed multisig transaction file to the microSD card.