Setting up a Trezor Model T Shamir’s Secret Sharing Backed-UpWallet to be Used in Conjunction with ElectrumSV
While the latest firmware 2.3.1 for Trezor Model T created some unrest for Electrum, ElectrumSV and ElectronCash users, the versions above 2.1.5 actually have a very useful feature.
You are able to set up new wallets using a Sahmir’s Secret Sharing Scheme. There are not so many wallets that let you do this in a user friendly way without using command line tools. This means that you can back up your wallet seed in a way where there is no single point of failure. So what does that mean? If we set up a 2/5 Sahmir’s Scheme, it means that any 2 of 5 shares of the backup are needed in order to restore the wallet. Many times more importantly it also means the wallet can still be restored even if 3 of 5 shares are lost e.g. in a destructive event like a fire or by theft, the wallet is still backed up safely. Trezor allows for setting up such a scheme with up to 16 shares and any threshold.
At this point I would like to point out that there are also low tech methods to basically do the same thing.
In order to set this up, I propose you have whatever current wallet you have on your Trezor properly backed up.
- Install Trezor Model T firmware 2.3.0 (not higher at this point).
2. Wipe your Trezor Device according to these instructions.
3. Set up a new Trezor wallet by going to:
“https://trezor.io/start/”
4. Choose Model T
5. Confirm the Message about the Seal of the USB C Port
6. Choose “Create Wallet”
7. Choose to create a wallet with Shamir Backup
8. Confirm this on your Model T. You should now see a message that the wallet was created. Choose “Back Up”
9. Confirm set number of shares
10. Continue to set threshold.
11. After setting threshold confirm that you will only back up these shares on paper and not electronically.
12. Write down the first share consisting of 20 words. Note, the order of words matter here.
13. After confirmation of writing down the words, there will be three checks to confirm you did so correctly
14. Continue for all subsequent shares until you get the final confirmation
15. You should also get confirmation that your backup is done now
16. Your device now shows this screen
17. Continue the setup process for your wallet in the web interface. Protect your device by PIN and give it a name. Please note that the Shamir Scheme is for backup only and does not create some sort of multi-signature setup.
18. Next open your ElectrumSV wallet and generate a new wallet. Protect it with a password if you want for privacy and extra security. Your keys will be protected inside the Trezor however (And by your sharded backup you just created)
19. Once the new wallet is set up press the “Add Account” button on the top left.
20. Choose “Import Hardware Wallet”
21. Select the Trezor which is still connected
22. Choose the derivation path. While ElectrumSV native wallets themselves do not use a coin identifier etc. in the derivation path, you should set one here. Since someone on GitHub once proposed we use 236 as the BSV coin-ID I will use this. If you set it to 145 you will get the same addresses as your BCH wallet in the Trezor online wallet will show you. You will also get the same xpub key as Trezor would give you for your BCH wallet. In case you have not split your coins yet (BCH/BSV) you should choose 145.
23. If you set a password for your ElectrumSV Wallet, you will need to enter it to confirm the wallet linking to the Trezor device.
24. You wallet is ready to receive coins.
If you want to test the wallet now, see the guide on signing with Trezor and ElectrumSV.
If you have trouble with the latest Trezor firmware, check this guide.