One of my most favorite ways of storing bitcoin is on a paper wallet. Paper wallets if done right are one of the most secure ways of storing bitcoin especially if done on an air gapped computer which in my opinion is a must.
The tricky part is when the time comes to sweep the wallet and that is where screwups can happen. If your computer or phone has a malware or virus infecting it, then chances are you can lose your bitcoin.
One way to prevent this from happening is to never expose your private key to a hot wallet or the internet, but rather have it signed using an airgapped device with a wallet on it.
We will be using Electrum and to make sure you have the right Electrum, you can read about it on this thread I wrote on another way of siging a BTC transaction where people brought up ways to make sure your electrum download is not tainted in anyway.
https://bitcointalksearch.org/topic/how-to-generate-a-signed-btc-transaction-using-electrum-and-trezor-5106013 www.electrum.org I will use cell air gapped cold wallet to cell hot wallet
So in this setup we will have a cellphone and a computer both installed with the latest version of Electrum.
These are the steps I took....
Wipe out all data on cellphone and have it reboot with factory reset, thus cleaning it of any malware or viruses.
Install Electrum and then place it in Airplane mode, disable wifi, disable bluetooth, remove sim card and also remove the antenna thus making it air gapped.
Creating new wallet as follows.....
Click NEXT then name your wallet
Next create new password
The select type of wallet you are creating..in our case we are importing a public or private key.
So up to this point you can use for both the air gapped and live hot phone electrums.
Click on the camera tab to scan the qr code.
Here I will be importing the
private key for the air gapped wallet phone
You can do the same for the HOT LIVE Cell phone wallet, BUT, ONLY IMPORT THE PUBLIC KEY!
On the air gapped phone the OFFLINE will show as there is no connection with any internet signal. Thats exaclty what we want to see.
When clicking receive on both phones, and then request, the public address matching THAT particular private key will show.
The Air gapped and the Hot phone Public addresses should both match!
On the HOW LIVE phone, click click scan and scan qr code of public address you want to send the paper wallet funds to
Then Click amount and send MAX. Always sweep a paper wallet fully!
You can set the mining fees on the app,
Change the method to "Static", you will be able to set the transaction fee to lower amounts.
Look at the image below. The fee is only 1 sat/byte.
Next click PAY and the following information will show. Here you can check amount of BTC sent, mining fee and most importantly BTC address where bitcoin is being sent
to.
Next click on QR tab and the following RAW UNISGNED TRANSACTION QR code comes up.
Now with your air gapped phone click on SCAN and scan the QR code from your live phone.
This will take your raw unsigned transaction into your cold air gapped phone with the private key to be able to be signed!
This is what will show on your air gapped phone after scanning the QR code from the LIVE HOT phone wallet.
Next click on the sign TAB and the following will come up confirming you want to sign the unsigned transaction.
Once you click on yes, the new window coming up will show you a signed BTC transaction with the address the btc is going to also the amount!
This way you can be sure the btc is going to the BTC address you want it to goto and not some malware altered BTC address!! Also the TX data is also present and
showing.
Now for the final steps of transferring this to your hot phone by clicking on the QR tab on the air gapped phone which will produce a QR code.
Take your live HOT Wallet phone and click on Scan, then scan the QR code from the Air gapped wallet.
The following will show up, and again you can confirm and the information. Once you are satisfied, click on Broadcast and the raw transaction will be broadcast on blockchain and the bitcoin will be transferred from your paper wallet to the BTC addy of your choice.
I hope this helps people understanding how a paper wallet can be swept without ever having to expose the private keys to a HOT wallet.
Again test with a very small amount of BTC until you have it nailed down and feel comfortable in doing this.
Made another visual aid to make it even easier to understand.
