Should I Upgrade?

[ps1234]

I've set up Electrum on an airgap computer and a watching wallet on my normal PC.

The versions are 3.3.8, but I see that there's a newer version 4.0.9.

I'd rather not touch the airgap PC, so can I run 4.0.9 on the watching PC and stick with 3.3.8 on the airgap?

Indeed, should I stick with 3.3.8?

[ranochigo]

If you want to upgrade to 4.0.1 and above, then you'll have to upgrade both instances. The raw transaction is no longer backwards compatible after they changed the format. [1]

[1] https://github.com/spesmilo/electrum/blob/ae15bccb8192532afc4908b43f68797cd6239fd6/RELEASE-NOTES#L123

[Oshosondy]

Why do you need to upgrade your cold electrum wallet, I do not think there is any need for that, only what you need to update is the watch only wallet, the cold electrum wallet is just for signing and nothing more than signing. But the watch only wallet will have the features you need to have on electrum, such as RBF and new features on latest versions.

[BrewMaster]

Why do you need to upgrade your cold electrum wallet, I do not think there is any need for that, only what you need to update is the watch only wallet, the cold electrum wallet is just for signing and nothing more than signing. But the watch only wallet will have the features you need to have on electrum, such as RBF and new features on latest versions.

RBF and similar features are not new features, they existed in electrum for a very long time. in fact i think electum was one of the first wallets to implement it.
also certain things change in major versions like 4.0 which requires you to update both cold and hot wallets at the same time because when you want to use your cold wallet to only sign it has to be able to recognize the raw transaction it receive, this format was changed in 4.0.

[ps1234]

also certain things change in major versions like 4.0 which requires you to update both cold and hot wallets at the same time because when you want to use your cold wallet to only sign it has to be able to recognize the raw transaction it receive, this format was changed in 4.0.

Thanks for the clarification.

As a follow on, let's suppose I stay with v3.3.8 and my airgap PC dies. I will have to start again by installing a new version on both the airgap and watching, but will my existing seed phrase still work? Or should I print off my private keys and sweep them in?

[BrewMaster]

will my existing seed phrase still work? Or should I print off my private keys and sweep them in?

no you don't have to do that. your seed is still valid because it is an important part of electrum project that even if it changes some day in the future they will keep the software backward compatible meaning you can can always use the "old" seed in the "new" software and get the same keys again.

[Dabs]

If you have more than one machine to test this one, maybe install the "upgrade" on the new machine, manually type in the seed phrase and you'll have the latest version on that new machine.

Then try moving around your coins or if you need to actually spend them, sign the transaction on the new airgap with upgraded software. If that works, then you can probably upgrade the other machine as well.

[ps1234]

I carried out a quick test, but I don't understand the results.

With Version 3.3.8 I created a new test wallet, noted the seed phrase, and exported the private keys as a CSV file.

With V 4.0.9 I created a new test wallet, used the above seed phrase, and exported the private keys as a CSV file.

In the resulting CSV files, V 3.3.8 exported 26 addresses and private keys. However, V 4.0.9 exported 30 addresses and private keys.

Comparing the 2 CSV files in Excel, the 26 addresses and private keys were identical in both versions, but V 4.0.9 generated 4 extra addresses and private keys.

Why the extra 4?

Forgive me lack of understanding, but if in V 3.3.8 I generate several new addresses, after the original 26, would new private keys result?

If so, and if I used the seed phrase to restore a wallet, how would it know that new private keys had been created?

Finally, can I assume that because v 4.0.9 generates 4 new private keys, then restoring a seed phrase from a V 4.0.9 wallet to recreate in V 3.3.8, then effectively, 4 private keys, and their associated addresses and bitcoins, would be lost?

[Dabs]

Private keys (and addresses) can be generated from the same seed phrase an unlimited number of times. Perhaps version 4.0.9 just made 4 more than version 3.3.8, but both wallets will generate the same one hundred or one thousand keys in sequence.

Before Cryptopia died, I had a bot that would make daily withdrawals from my account there, and I fed it like a few dozen addresses from my Electrum wallet. The bot was trading an alt coin, selling it for bitcoin, then withdrawing the balance to my wallet once a day or if it reached a certain threshold I set.

You can also use just the master public key and generate the same list of addresses for that wallet, so you can watch them all.

What you are seeing with the two different versions may be a difference in the default gap-limit or something. Make them generate a few hundred addresses each, you will find they are all identical.

[ranochigo]

Why the extra 4?

The gap limit for the change address was changed from 6 to 10, between 3.3.8 and 4.0.1. It wasn't reflected in the Release Notes but I compared the changes in the codes previously.

Forgive me lack of understanding, but if in V 3.3.8 I generate several new addresses, after the original 26, would new private keys result?

No. Your seed phrase provides you with a master key pair, both master public key and master private key. The subsequent addresses or private keys that are generated from the corresponding keypair should not deviate no matter how many keys you generate.

If so, and if I used the seed phrase to restore a wallet, how would it know that new private keys had been created?

When you restore a wallet, Electrum will start to generate addresses until it hits a gap limit, that is if it finds at least 20 "receiving" addresses that has never been used and 10 "change" addresses that has never been used. If you were to change the gap limit and use the addresses out of sequence, you'll have to modify the gap limit to ensure that Electrum manages to generate that many addresses.

Finally, can I assume that because v 4.0.9 generates 4 new private keys, then restoring a seed phrase from a V 4.0.9 wallet to recreate in V 3.3.8, then effectively, 4 private keys, and their associated addresses and bitcoins, would be lost?

No, the software should never generate addresses which doesn't belong to the seed phrase or the master public key that you have imported. Both wallets will generate the addresses similarly as Electrum seeds has a version byte which tells the software the types of keys to generate so that it won't generate a legacy address (1) if you have used a Segwit address(bc1) before and vice-versa.

[o_e_l_e_o]

If you go in to both your wallets, open the console (you might need to click on View -> Show Console first), and then enter the following command:

Code:

wallet.gap_limit_for_change

You will see that one displays 6 and the other displays 10, as ranochigo has explained. There is no easy command to increase the gap limit for change address like there is for receiving addresses as far as I am aware, but you can use the following command (again, in the console) to generate 4 more change address beyond the gap limit:

Code:

for i in range(0, 4): wallet.create_new_address(True)

Do that and then re-export your private keys to satisfy yourself that they do indeed all match up.

[ranochigo]

If you go in to both your wallets, open the console (you might need to click on View -> Show Console first), and then enter the following command:

Code:

wallet.gap_limit_for_change

There is no easy command to increase the gap limit for change address like there is for receiving addresses as far as I am aware

You actually mentioned the command needed to do so yourself 

Code:

 wallet.gap_limit_for_change = X

. Just replace X with the gap limit.

[o_e_l_e_o]

Huh. Didn't realize it was that simple, haha. I'm sure I remember trying that and being met with an error before. Or maybe I was trying variations of wallet.change_gap_limit(10).

Still, it doesn't really make sense to increase you gap limit for change addresses since you shouldn't really be manually interacting with these addresses, handing them out, skipping addresses, etc. Just let Electrum handle your change for you.

[Dabs]

I think, if you messed up, and generated like 200 addresses, and used something in the middle (the 50th or 100th address) and skipped the first 20, ... either make sure to end up using the first 20 in order, or just start over with a new wallet and move your coins over to the first address. Or if using coin control, each input goes to the first few addresses in order.

I would just as likely consolidate everything just to save on fees, privacy be damned, most people don't really care that much.