Offline signing of HW multisig

[Espen11]

Hi, I'm having trouble with a multisig setup using HW wallets and an offline computer for signing.

I have created a transaction on an online watch-only wallet and transferred it to the offline computer for signing with one of the HW wallets. I then get this error:
"no interface to do request on... gave up"

https://imgur.com/a/uBdmZJY

I can trace it to line 727 here: https://github.com/spesmilo/electrum/blob/master/electrum/network.py
It looks like it's failing since I'm offline. But that's the whole point.

Anyone else got this? Or can help me?


Edit: Electrum 3.3.2 btw...

[Espen11]

Hmm...
Looks like I solved it. The electrum wallet file needed to touch the internet. A bit strange.

My setup was:
One online laptop and one offline laptop.
Three HW wallets.
The offline laptop and the three HW wallets have never touched the internet.

I created a 2 of 3 segwit multisig wallet on the offline machine with the three HW wallets and added the public watch-only key to the online machine.
Then I sent some bitcoin to it.

I then created a transaction with the online watch-only key and let the offline laptop scan the QR code for the transaction and signed the transaction with the private-keys on the HW wallets. This gave me the "no interface" error described above.

The solution was to copy the Electrum wallet file from the offline computer to the online computer and let it sync (over tor to my electrum server and full node). I did not connect any of the HW wallets and did not interact with it at all. Only opened Electrum, let it sync, and closed it.

When I transferred the wallet file back to my offline computer it all worked. No idea why.

Does the wallet-file need to initialize or something?
Could someone explain me why this occurs?

[HCP]

My guess would be that it is the Hardware Wallet plugin attempting to connect and failing because the computer is offline...

Most likely because the HW wallets like to connect and refresh transactions/balance on startup. You might get a better response if you post your query on the Electrum Github issues list if you haven't already.

[Abdussamad]

AFAIK hardware wallets aren't designed for offline use. They are designed to make securing and handling your bitcoin easy i.e. without having to resort to cumbersome offline wallets. I'm guessing it worked after the sync because electrum now had data related to your unspent outputs. Data that it can only get from the blockchain.

If you want to resort to offline storage then you have no need for an HW. Electrum can do that for you for free.

[HCP]

I'd have to agree... combing HW, multi-sig and airgapping seems like total overkill... especially given that HW are designed to be used (safely) in an online environment.

[Espen11]

I know it's not design for it. I'm just seeing what's possible.

Overkill... well.. Would be cool to have a 100% air gapped solution where neither the keystore nor the computer has touched the internet (and still make it a 2min job to use it).
And yeah, I could just use regular computers without the HW wallets, but then the key is exposed to Linux and electrum with all it's unknown dependencies. So just in case it ever got online the key is still safe.

Coldcard could simplify tho... But all my HW wallets are from different vendors, so I like to have options