Combining Blue Wallet and a watch-only Electrum wallet

[unknowncustomer]

Hello,

In order to increase privacy/security, I expect to:

- Buy an old iPhone, download Blue Wallet app, setup the iphone on airplane mode forever
- Create a seed on the Blue Wallet app, store the seed in a safe place
- Create a watch only wallet on Electrum linked to the Master Public Key of the Blue Wallet seed.
- Send my btc through the watch only wallet

Is it optimum ?
Will I be able to send and receive btc thanks to the watch only wallet and my offline wallet (Blue Wallet) ?

Thanks!

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[khaled0111]

Will I be able to send and receive btc thanks to the watch only wallet and my offline wallet (Blue Wallet) ?

Yes, just make sure to download both wallets from their official websites, store your wallet's seed in a safe place and never connect your iphone to the Internet (to import/export unsigned/signed transactions, use QR codes).

Use the watch-only wallet (electrum) to monitor your addresses activities and to create your transaction -> export it to the offline wallet (blue wallet) -> sign it -> import the signed trandaction into electrum -> broadcast it.

Here is a quick guide from made by bluewallet explaining how to sign transactions offline:
https://bluewallet.io/docs/sign-offline/

[NeuroticFish]

Watch-only wallet does not contain your private key, you can not spend using such wallet, only used for tracking your transactions.

I think that OP meant to use the old iPhone as cold storage, create the transactions with the watch only wallet, sign with the iPhone, broadcast with the watch only wallet. Doable.

@unknowncustomer , I've made a topic on pretty much the same use case, there are pluses and minuses, I recommend you read through all the answers there: Old phone as cold storage?; you could start with post #4 there.

[hosseinimr93]

With generating the seed phrase offline (assuming the old iPhone is clean and there is no malware in it), you can increase your security, but you don't really increase your privacy.

When it comes to your privacy in electrum, there is no difference between a wallet including private keys and a watch-only wallet. In both cases, you connect to a server to get data.
The server you connect to can know all the addresses belong to the same person and also link them with your IP.

[Charles-Tim]

In order to increase privacy/security, I expected to:

Having cold storage for signing transaction from watch-only wallet is more secure and safe, but know that it does not add to privacy. To have privacy, you will need to run your own node using Tor connection.

I think that OP meant to use the old iPhone as cold storage, create the transactions with the watch only wallet, sign with the iPhone, broadcast with the watch only wallet. Doable.

Having watch-only wallet for making unsigned transaction and transferring the unsigned transaction to be signed on cold storage airgapped wallet is possible as long as the seed phrase generated by the wallet on cold storage generates the master public key imported on the watch-only wallet. You are definitely right

[unknowncustomer]

This is exactly where I want to go.
- I guess it is possible to generate a seed through blue wallet or electrum even though these devices are not connected to the internet ?
- Can you confirm that if I lose both devices (the offline one and the online watch-only wallet) my heirs can retrieve my btc if I give them my seed phrase (and that they will be able to spend these btc) ?

[hosseinimr93]

- I guess it is possible to generate a seed through blue wallet or electrum even though these devices are not connected to the internet ?

Right.
The seed phrase is derived from a random number through some mathematical calculations in your device and there is no need to internet connection for that.

- Can you confirm that if I lose both devices (the offline one and the online watch-only wallet) my heirs can retrieve my btc if I give them my seed phrase (and that they will be able to spend these btc) ?

Right.
All your private keys can be derived from your seed phrase and that's all you need to recover your fund.

[khaled0111]

- I guess it is possible to generate a seed through blue wallet or electrum even though these devices are not connected to the internet ?

Yes you can and you must generate the seed offline if you want to use your wallet as cold storage.

- Can you confirm that if I lose both devices (the offline one and the online watch-only wallet) my heirs can retrieve my btc if I give them my seed phrase (and that they will be able to spend these btc) ?

Yes, you are right. The seed is all you need to recover your wallet so make sure not to lose it.
Note: blue wallet afaik follows the bip39 standard to generate seeds while electrum uses its own standard. So, you can't use blue wallet to recover a wallet generated by electrum from seed.

[hosseinimr93]

Note: blue wallet afaik follows the bip39 standard to generate seeds while electrum uses its own standard. So, you can't use blue wallet to recover a wallet generated by electrum from seed.

Bluewallet use BIP39 standard for generating a seed phrase. But it can be used for recovering a wallet using the seed phrase generated by electrum as well.
There's just a requirement. The wallet must have been funded. If there is no used address in the wallet generated by electrum, you can't import it into bluewallet.

[Abdussamad]

This is just asking for trouble. For fool proof operation you should use the same software on both online and offline devices. I suggest you buy a used desktop or laptop instead and install electrum on that.

[Charles-Tim]

Yes, you are right. The seed is all you need to recover your wallet so make sure not to lose it.
Note: blue wallet afaik follows the bip39 standard to generate seeds while electrum uses its own standard. So, you can't use blue wallet to recover a wallet generated by electrum from seed.

The cold storage wallet is on Bluewallet, while the watch-only is on Electrum. Bluewallet is BIP39. It can be recovered easily on Bluewallet, or if want to use Electrum, the BIP39 box will be checked if importing seed phrase on it.

There's just a requirement. The wallet must have been funded. If there is no used address in the wallet generated by electrum, you can't import it into bluewallet.

I imported a seed phrase from Electrum wallet to Bluewallet, any of the address of the Electrum wallet has not received any coin before, they both have the same keys and addresses, Bluewallet generated it without any address funded before importing the seed phrase.

This is just asking for trouble. For fool proof operation you should use the same software on both online and offline devices. I suggest you buy a used desktop or laptop instead and install electrum on that.

I too will consider this a good step to follow. But making sure he reinstall the OS himself and make it airgapped. I do not know why he wants to make use of two wallets when Electrum is perfect for both cold storage and watch-only.

[hosseinimr93]

I imported a seed phrase from Electrum wallet to Bluewallet, any of the address of the Electrum wallet has not received any coin before, they both have the same keys and addresses, Bluewallet generated it without any address funded before importing the seed phrase.

You are right. I just tested it with a fresh electrum wallet and it worked. I remember it was not possible to import a wallet generated by electrum into bluewallet if there was no used address in the wallet.
Something has probably changed in the latest versions of bluewallet.

I do not know why he wants to make use of two wallets when Electrum is perfect for both cold storage and watch-only.

That may be because electrum doesn't support IOS.

[unknowncustomer]

Yes because for me air gapping an iPhone or Android is easier than a PC or MacBook, maybe you have tips for airgapping a device in an easily manner ?

[LoyceMobile]

Yes because for me air gapping an iPhone or Android is easier than a PC or MacBook, maybe you have tips for airgapping a device in an easily manner ?

Get a laptop, download Tails OS, burn it on a DVD, remove the hard drive and network card if you want, then boot the laptop from the DVD. You could use an USB stick instead, but those aren't read only.
Tails is designed to be private. Even better if you don't give it internet access.

[NeuroticFish]

You could use an USB stick instead, but those aren't read only.

Tails by default doesn't allow persistence, so, unless he doesn't play with things he shouldn't, he should be fine even with an USB stick.

[Pmalek]

Yes because for me air gapping an iPhone or Android is easier than a PC or MacBook, maybe you have tips for airgapping a device in an easily manner?

Turning on airplane mode or not connecting your phone to WIFI or using mobile data isn't really an airgapped device. The device losses that feature if you or someone else accidently turn any of those network antennas on.

A properly airgapped device can't be connected to the internet because the necessary hardware has been removed, such as WIFI/network card. It's therefore easier to set up a properly airgapped PC than it is to do the same on a phone. I don't believe I have ever come across a tutorial explaining how to airgap a phone properly. 

[o_e_l_e_o]

I don't believe I have ever come across a tutorial explaining how to airgap a phone properly.

Unless you have a modular phone which you can open up and physically remove all the necessary hardware, then you cannot reliably airgap a phone. The whole purpose of a phone is to be able to communicate in a variety of ways - radio, WiFi, Bluetooth, NFC, RFID, etc. Trying to take such a device and stop it from communicating at all is an impossible task. Turning on airplane mode will help, but even while airplane mode is turned on different phones still constantly communicate with their environment through a variety of ways. How effective airplane mode is will depend very much on your model of phone. Airplane mode is not airgapped mode.

Far easier to take an old laptop whose only means of communicating is via WiFi and open it up and remove the WiFi card.