Easy wallet export to mobile (first gen.)

[mvaivre]

Linked to #183.

Idea : we could encrypt the mnemonic and encode the resulting string in a QR code. Scanning this on the mobile wallet would ask the user for the same password used on the desktop wallet to encrypt the key.
If the password is correct, the wallet is recovered.

We could experiment with adding the metadata in the QR Code as well.

Let's see if we could ship this in 2.0.

[nop33]

Since the password is not stored anywhere, the user would need to enter their password in order to encrypt the mnemonic and show the QR code. Actually, it won't have to be the same password. As long as the same password is used to encrypt the unencrypted mnemonic on the desktop wallet side, and the same password is used on the mobile wallet on the decrypting side, it will work. It could just be a temporary password, just for the transfer of the mnemonic. I like this approach more, personally, so that the user doesn't have to add their desktop wallet password on the mobile wallet (in principal, a password should not be used in more than 1 place, and for one purpose).

On a second note, do you think it's really necessary to encrypt the mnemonic before showing it in the QR code?

[mvaivre]

1. On the "temporary password" idea : it may be hard to explain the concept to the user. The less passwords the better. But let me clarify what I'm suggesting here:

• User shows the "export QR code" on the desktop by entering their usual password, as they do when they want to display the mnemonic or simply enter the wallet.
• On the mobile, the user scan the code and enter the password used on the desktop only once to allow decrypting the mnemonic and restoring the wallet. The password isn't stored nor used on the mobile. It's used only when restoring.

On a second note, do you think it's really necessary to encrypt the mnemonic before showing it in the QR code?

Yes. If for whatever reason a user displays the qr code in a public place (this can happen easily when playing with the app in a train or in a coffee...), anyone could snap a picture from afar and get the mnemonic. So easy.

[nop33]

This was implemented in #440 and merged into the v2.0 branch, it can be closed.