Is there any way to add a change address to Electrum Offline Android wallet?

[deepcolderwallet]

Situation: Using latest Electrum android version I have an online smartphone that has the xpub but not the seed. This wallet has received some change on a specific address that I'd like to import to Jaxx. The seed owner, an offline cryptographed smartphone won't show that address in it's address list (because it was generated deterministically).

Question: Is there any way I can fetch that change address to the offline smartphone so I can export it's private key?

Thanks.

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[LoyceV]

I think what you're looking for is to increase the Gap Limit, see How can I pre-generate new addresses?:

Code:

[wallet.create_new_address(False) for i in range(50)]

(read reference link first!)

I've never used Electrum on Android, so I'm not sure if it has a console to enter this.

[HCP]

I've never used Electrum on Android, so I'm not sure if it has a console to enter this.

As far as I'm aware, there isn't a way to increase the gap limit on the android version as there is no console

Question: Is there any way I can fetch that change address to the offline smartphone so I can export it's private key?

Another way that I can think of to get your private key would require that you use the seed and something like the Electrum Seed Tester: https://github.com/FarCanary/ElectrumSeedTester

You just need the "standalone" .html file. Using that you could find the required change address and matching private key. The trick is how to do that in an "offline" manner. If you had an OTG cable for your offline smartphone, you could transfer it via a USB stick.

Or, alternatively, you could setup an offline PC and install the desktop version of Electrum, restore from your Electrum seed and then you'll be able to increase the gap limit and/or manually generate change addresses until you find the one you want.

Failing that, another (more expensive) option would be to go into the Electrum address list (receive tab, tap the address shown), then tap the "receive" button to change the filter to show "change" addresses, then select the last one in the list and select "use". Then send some coins to that address. It might force the wallet to generate more addresses. NOTE: I can't test this method as there isn't a TestNet version of the Android wallet available, so I can't guarantee that it will actually work.

[Abdussamad]

I think what you're looking for is to increase the Gap Limit, see How can I pre-generate new addresses?:

Code:

[wallet.create_new_address(False) for i in range(50)]

(read reference link first!)

I've never used Electrum on Android, so I'm not sure if it has a console to enter this.

Actually you have to pass True to that function for change addresses.

@OP I suggest you restore from seed on an offline PC and then do the cold storage dance:

http://docs.electrum.org/en/latest/coldstorage.html

This is the way to spend from cold storage in electrum.

If you insist on exporting the private key then understand that knowledge of the private key + your xpub gives an attacker complete access to your wallet. So it is not safe. But if you want to do it anyway then you will still need to restore from seed on an offline PC, run the command LoyceV gave you (with the small modification I mentioned above) until that address shows up in your wallet (how to check). Then simply right click on it on the addresses tab (view > show addresses) and choose to view the priv key

[deepcolderwallet]

Thank you, guys. Actually none of these solutions meets the requirement of using only the two mentioned smartphones. I think generating randomly adressess at the offline phone might do the trick.

If you insist on exporting the private key then understand that knowledge of the private key + your xpub gives an attacker complete access to your wallet. So it is not safe.

Actually it's not on my plans to disclose the xpub. Also I don't see how an attacker could have complete access to my wallet having knowledge of only one address's priv key. The other addressess's priv keys and the seed will be safe, right?

My first thought was that Electrum Android would have a feature that would solve this situation.

Thank you all once more.
If I had any smerit left, it'd be yours.

EDIT: Grammar and layout.

[Abdussamad]

If you have any one address' private key and the xpub you can recover the private keys of all the addresses in the electrum wallet.

[deepcolderwallet]

If you have any one address' private key and the xpub you can recover the private keys of all the addresses in the electrum wallet.

That's new to me!
Do you have any source where I can dive deeper in this subject?

[LoyceV]

If you have any one address' private key and the xpub you can recover the private keys of all the addresses in the electrum wallet.

That's new to me!
Do you have any source where I can dive deeper in this subject?

See for example: Keep in mind: XPUB and one private key will expose all private keys in the same HD wallet!!!:

This should be shown in RED CAPITAL LETTERS every time anyone creates a new HD wallet!!! I have been storing my bitcoins for years thinking they would be secure in my cold storage and never cared about compromized private keys of old addresses with zero balance. I've been lately throwing the priv keys of used addresses left and right to claim all airdrops/forks thinking that if the address does not have any BTC anymore, leaking its private key cannot cause any harm. I have also stored my xpub key on all my devices unencrypted to create watch-only wallets (any malware/hacker could have captured BOTH)

On the same page user largely_useless adds this:

Keep in mind that this only goes for unhardened derivation. BIP44/49 uses hardened derivation on the account level, so the risk is limited to only the funds in the compromised account.

[HCP]

Is it a specific requirement to "import" the private key into Jaxx? As mentioned with an xpub and a private key, the entire chain in that "account" could be compromised.

Would you not be better off simply sending those funds to Jaxx using the standard protocol?

Also, have you tried simply creating an unsigned transaction on the Electrum watching only wallet that includes the funds from the change address and then tried importing that unsigned transaction into the offline Electrum? This might trigger the offline wallet into "generating" the change address that you require.

[deepcolderwallet]

Is it a specific requirement to "import" the private key into Jaxx? As mentioned with an xpub and a private key, the entire chain in that "account" could be compromised.

Would you not be better off simply sending those funds to Jaxx using the standard protocol?

Also, have you tried simply creating an unsigned transaction on the Electrum watching only wallet that includes the funds from the change address and then tried importing that unsigned transaction into the offline Electrum? This might trigger the offline wallet into "generating" the change address that you require.

Would be a solution IF Electrum Android allowed me to create a transaction using an specific address, which it doesn't. The ANDROID watch-only wallet has no option to spend from that specific address, or does it?

[deepcolderwallet]

If you have any one address' private key and the xpub you can recover the private keys of all the addresses in the electrum wallet.

That's new to me!
Do you have any source where I can dive deeper in this subject?

See for example: Keep in mind: XPUB and one private key will expose all private keys in the same HD wallet!!!:

This should be shown in RED CAPITAL LETTERS every time anyone creates a new HD wallet!!! I have been storing my bitcoins for years thinking they would be secure in my cold storage and never cared about compromized private keys of old addresses with zero balance. I've been lately throwing the priv keys of used addresses left and right to claim all airdrops/forks thinking that if the address does not have any BTC anymore, leaking its private key cannot cause any harm. I have also stored my xpub key on all my devices unencrypted to create watch-only wallets (any malware/hacker could have captured BOTH)

On the same page user largely_useless adds this:

Keep in mind that this only goes for unhardened derivation. BIP44/49 uses hardened derivation on the account level, so the risk is limited to only the funds in the compromised account.

Thank you very much. I wish I had smerit to reward you.

[nc50lc]

Would be a solution IF Electrum Android allowed me to create a transaction using an specific address, which it doesn't. The ANDROID watch-only wallet has no option to spend from that specific address, or does it?

So, it's for verification then? Android version can't do that.

You can just create a "watch-only single address wallet" in your PC and create the unsigned raw transaction,
then import it to your cold storage Android Phone for signing.
If you don't have a PC, you can ask someone to create the raw Tx for you as they will only need that change address and the recipient's address.

Or is this an implicit feature request for Android version?

[HCP]

Would be a solution IF Electrum Android allowed me to create a transaction using an specific address, which it doesn't. The ANDROID watch-only wallet has no option to spend from that specific address, or does it?

If you can't (and I'm fairly you can't) specify a specific UTXO to spend or choose a specific address to spend from, you could just create a "dummy" transaction that spends your entire balance. That way it is guaranteed that the change address will be included.

[deepcolderwallet]

Would be a solution IF Electrum Android allowed me to create a transaction using an specific address, which it doesn't. The ANDROID watch-only wallet has no option to spend from that specific address, or does it?

So, it's for verification then? Android version can't do that.

You can just create a "watch-only single address wallet" in your PC and create the unsigned raw transaction,
then import it to your cold storage Android Phone for signing.
If you don't have a PC, you can ask someone to create the raw Tx for you as they will only need that change address and the recipient's address.

Or is this an implicit feature request for Android version?

Perfect!

Gotta try this.

Thank you!


EDIT: I created a new watch-only wallet on the Android version itself, and could create the unsigned transaction from there. Simple and easy. Thanks once more, bro.