Is it possible to broadcast a Tx while Electrum is offline? [Answered]

[AB de Royse777]

This could be a stupid question to ask but lately I am thinking:

1. Create a wallet while my device is not connected online.
2. Save the seed somewhere offline.
3. Send some funds from my mobile device to this new wallet while offline.
4. Send the funds back to the mobile device.

At some point I need to connect the laptop to internet because I can not do the boardcast and can not see balance update without connecting online.

Question: How can I do both by exposing me less to the internet?
Or is there any way not to expose the wallet with an online device at all?

Cheers,

[bob123]

1. Create a wallet while my device is not connected online.
2. Save the seed somewhere offline.

You shouldn't be doing that.
Instead, generate your seed and mnemonic code while being offline.

You could just use a usb-bootable linux distro with electrum (verify the signature) to create your seed completely offline.


Further, it also is not necessary to go online with the device containing the private keys.
You can use a watch-only wallet on your online device. Just import the master public key into your online electrum wallet. You will see your balance and can create new addresses. You just can't spend from them.
With this watch-only wallet you are able to create unsigned transactions, move them to your offline device, sign them there and move them back to your online device.

This way your private keys are never exposed on an network-connected device.

[AB de Royse777]

Just import the master public key into your online electrum wallet.

Just to double check.

Wallet > Information > I get the master public key

Please confirm

I can restore the wallet with this public key but it's a watch only wallet and I can have it in the online device. I think I have a clear idea now.

[bob123]

Just to double check.

Wallet > Information > I get the master public key

Please confirm

Yes.

I can restore the wallet with this public key but it's a watch only wallet and I can have it in the online device. I think I have a clear idea now.

Yes. This watch-only wallet will only allow you to derive public keys (and addresses). This means you can see the whole balance, generate new addresses and create unsigned transactions.

You basically want to use that wallet for:

• Creating a new address
• Checking you received a transaction
• Create an unsigned transaction
• Broadcast the signed transaction

Your offline wallet (containing the private keys) does:

• Sign the unsigned transaction

[AB de Royse777]

Your offline wallet (containing the private keys) does:

• Sign the unsigned transaction

And logically my offline wallet will always show the addresses that it generated initially when it was created and will always show zero balance which is nothing to be worried by just looking at it :-P

I think I have all info that I wanted and verified. If you have anything to add up then please do. I will lock the topic very soon.

Cheers bud.

[NeuroticFish]

Just to double check.

From what I see you want to do cold storage? The first post is wrong, you should start with reading:
https://electrum.readthedocs.io/en/latest/coldstorage.html

The seed wallet stays always offline; you can use it only to sign transactions.
The live/online wallet is used to see the actual amounts of money, create transactions (unsigned), broadcast (after signing on the other wallet).

[AB de Royse777]

From what I see you want to do cold storage?

Pretty much this is it. I knew the term cold storage but  I never looked it that way. This just popped into my mind and was looking for the solution. I am glad that I now know a little more about my security :-D

Thanks buddy to both you and bob.

[o_e_l_e_o]

And logically my offline wallet will always show the addresses that it generated initially when it was created and will always show zero balance which is nothing to be worried by just looking at it

Correct. Your offline wallet will always show zero balance because it never connects to the internet, never receives updated information from the network, never receives any new blocks, never sees any confirmed transactions, and so on. All it does is sign the unsigned transactions you generated on your watch only wallet.

Your offline wallet will also show all the addresses it initially generated, but like any wallet, can generate as many more addresses as you need. Given that you are using the master public key from that wallet to generate your online watch only wallet, all the addresses generated by both wallets will be the same.

[u9y42]

From what I see you want to do cold storage?

Pretty much this is it. I knew the term cold storage but  I never looked it that way. This just popped into my mind and was looking for the solution. I am glad that I now know a little more about my security :-D

Thanks buddy to both you and bob.

And, depending on your setup, you can also use QR codes to send the (un/signed) transactions back and forth (with, say, a webcam connected to your offline computer plus a phone with the online wallet) to further minimize the connection between the two.

[AB de Royse777]

Thanks everyone for contributing on this thread. Shamefully it was a new experience for me but honestly speaking we all learn at some point. bob123 was really helpful here. His first reply solved every thing for me, rest were just extensions. Thanks u9y42, NeuroticFish and Leo for your inputs too. One way or other - all of them had some information.

Locking the topic.

Cheers,