Hi eveybody,
I will describe here how I made a "cold wallet". I would be very happy with suggestions and feedbacks about anything wrong (insecure) in my setup.
First I flashed tails in a USB drive, using the downloaded file from https://tails.boum.org/ . After downloading the file I checked the checksum provided by them to certify the downloaded file was legitime.
After flashing, I booted my laptop with the USB with Tails. After opening Tails, I did not connect to the Wifi, so I opened Electrum software. Then, I created a new wallet and Electrum showed me the 12 word seed which I wrote in a piece of paper far from any camera. After creating the wallet I opened the Xpub key and imported that as a watch-only wallet in the Blue Wallet android app. Then I just turned off Tails and my laptop...
I bought a metal plate
in which I engraved the seed as described in their manual... It is a coded BIP39 transforming the words in numbers based on the complete list.
Now I burned the paper so the seed is only in my head and the metal plate. The paper was never accessible to anyone or in front of any camera.
I put the metal plate in a secret place where only my wife knows, but she doesn't know how to decodify that yet... In case the metal plate is compromised somehow (for instance: someone discovers the place where it is hidden, or suspect anyone has seen that), which I think is very unlikely, I plan to move the BTC from that cold to another one...
Soon I plan to buy a Coldcard, but that is what I have now.....
Grateful for any comments...