transferring my coins from electrum hot wallet to electrum cold wallet

[BlockCheney]

I am planning to transfer my complete bitcoins from an electrum hot wallet to a cold wallet. My question is: can I just create a new receiving address in the read only part of the cold wallet which is online and then sent my coins to that address from the hot wallet?
And afterwards, how do I update the coins on my off-line machine So it shows the same amount of coins as on the read-only part?
Really want to be sure I don’t make a mistake there and lose my coins somehow

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[BlackHatCoiner]

My question is: can I just create a new receiving address in the read only part of the cold wallet which is online

A cold wallet is referred as “cold”, because it's disconnected from the internet. I guess that you consider it cold, because it's watch-only. Yeah, that may be true, there isn't a standard definition for “cold wallet”, anyway. To answer your question, yes you can create a new receiving address from the cold wallet, transfer it to the input field of the “hot electrum” and then broadcast that transaction.

And afterwards, how do I update the coins on my off-line machine So it shows the same amount of coins as on the read-only part?

Didn't you say that the “cold wallet” is online? If it is, it'll update your balance.

Read the answer below.

[o_e_l_e_o]

My question is: can I just create a new receiving address in the read only part of the cold wallet which is online and then sent my coins to that address from the hot wallet?

Yes. Provided you are certain that your online watch only wallet is indeed showing the same addresses as your offline cold wallet, which will be the case if you exported the master public key from your cold wallet as you should have done, then any new addresses you generate on your online watch only wallet will also be generated in the same order by your offline cold wallet.

And afterwards, how do I update the coins on my off-line machine So it shows the same amount of coins as on the read-only part?

You generally don't. You only need to see an up-to-date balance on the watch only wallet. You use the watch only wallet to create an unsigned transaction, and then move that unsigned transaction to your offline cold wallet to be signed. The offline cold wallet does not need to know the up-to-date balance of the addresses in it. As long as it has the private keys, it will sign the transactions without any issue.

[ranochigo]

My question is: can I just create a new receiving address in the read only part of the cold wallet which is online and then sent my coins to that address from the hot wallet?

The others are all answered well except for this. Generally, it is okay for someone to assume that the address corresponds to the one that you control. That is, assuming nothing is actively changing the address you're seeing and/or your clipboard. I would assume the worst and attempt to cross-check the address on my cold wallet as well, just a simple validation to check if I'm really sending to the correct address.

The purpose of your online wallet is to check for balance as well as to create a transaction. There is no protection if you've downloaded a malicious version on your online computer or if a malware can change the addresses in your online Electrum instance.

[BlockCheney]

Okay thanks that's what I needed to know. So I can either create the receiving address from the off-line machine or from the read only part of the wallet which is online?

[BlackHatCoiner]

Okay thanks that's what I needed to know. So I can either create the receiving address from the off-line machine or from the read only part of the wallet which is online?

As long as you've verified the authenticity of both, you can get the receiving address from any of them.

[o_e_l_e_o]

So I can either create the receiving address from the off-line machine or from the read only part of the wallet which is online?

Technically, yes. Practically, the best practice would be to create it from the watch only wallet, copy and paste it in to the "send" field of your Electrum hot wallet, bring up the advanced preview, then double check the address manually against your cold wallet to ensure it matches prior to hitting "Sign" or "Broadcast". This minimize the chances of any clipboard malware or a malicious version of Electrum changing your address without you noticing.

[BlockCheney]

Okay 👍 And in case that my off-line wallet machine is not working anymore, can I still recover my complete bitcoin balance using the seedphrase which I created on the off-line machine in the beginning?

[BlackHatCoiner]

Okay 👍 And in case that my off-line wallet machine is not working anymore, can I still recover my complete bitcoin balance using the seedphrase which I created on the off-line machine in the beginning?

Yes.

[o_e_l_e_o]

And in case that my off-line wallet machine is not working anymore, can I still recover my complete bitcoin balance using the seedphrase which I created on the off-line machine in the beginning?

Yes, plus any additional seed extension words you may or may not have chosen when you set up your wallet. (You had to click on "Options" and then check a box marked "Extended this seed with custom words". If you did this, you also need these words in addition to your seed phrase to recover your bitcoin. If you didn't do this, then don't worry about it, and your seed phrase is all you need.)

Bear in mind that if you are recovering your seed phrase to an online computer, rather than another offline computer, then your wallet is no longer a cold wallet and is at the same risk as any other hot wallet.

[nc50lc]

-snip- So I can either create the receiving address from the off-line machine or from the read only part of the wallet which is online?

If your cold-storage set-up isn't new or after using it once:
You need to always get a receiving address from the online watch-only wallet to be sure that the one you get isn't already used.
The offline wallet can't know which addresses was used so it might display the same address in the 'receive' tab over and over again.
(guessing you already know the privacy implications of reusing addresses)

[ranochigo]

Okay thanks that's what I needed to know. So I can either create the receiving address from the off-line machine or from the read only part of the wallet which is online?

As far as possible, try to check the addresses on both your main and offline instances; just the first and last few characters will be sufficient.

Master public key will provide zero deviation from both your wallets provided the same parameters but as I have mentioned, nothing can stop a malware on your online computer to change the addresses on it. The addresses that is displayed on your cold wallet will always be correct, but there are still quite a few attack vectors present on your online computer. I'm not sure if I'm being overly concerned about this or not.

You might need to increase the gap limit on your offline computer if someday you don't see the addresses being displayed on your offline computer.

[o_e_l_e_o]

I'm not sure if I'm being overly concerned about this or not.

I don't think you are. The whole point of airgapped cold storage is to be as secure as possible, right? You trade off the convenience of being able to send coins in seconds from a mobile wallet or a hot wallet for the added security of keeping your private keys permanently offline. Well, this security applies to both sending and receiving, I think. Just as you obviously have to use your airgapped wallet and not just your watch only wallet when sending coins, I think it is good practice to also check with your airgapped wallet when receiving coins. I'm not interacting with my cold storage on a daily basis like I am with my hot wallets, and so the added two minutes to boot it up and double check the address is a small price to pay for the added peace of mind.

If you really can't be bothered to boot it up every time, then I suppose you could boot it up and write down the next 5 or so receiving addresses on paper and keep them somewhere safe. Then, when you want to generate a new address from your watch only wallet, you can immediately check against your piece of paper that the address is correct. Only risk here is compromising your privacy if someone finds your piece of paper.