Bitcoin Forum

I'm looking at Tails (https://tails.boum.org/ (https://tails.boum.org/)) to make an offline wallet as described here: http://docs.electrum.org/en/latest/coldstorage.html (http://docs.electrum.org/en/latest/coldstorage.html)) for some BTC. Tails system has Electrum included, but the version is a year old, 2.7.9. I have successfully created an offline wallet, exported public key and made a watching-only online wallet on my main system. It seems to be working, but are there any potential problems with using an old Electrum version? Obviously, at some time in the future I will want to move the coins from it. Will the described procedure (create an unsigned transaction, sign, broadcast) work or will I have to recreate the wallet using the seed?

It should work fine for you. Any bugs should be deleted by the fact it's not online. As long as you use a higher version on your computer.
One thing to consider, you won't be able to use segwit as those transactions are signed differently.

Obviously if you can update the wallet, you should always try to, but if you want to keep your operating system fully sandboxed then that might not be an option as you'll either need the Internet directly or have to place an executable directly onto the sandboxed machine.

I'm aware of Segwit, but it is going to be a wallet for (relatively) long-term holding, not spending, so it should not be a problem. Current fees and transaction times are worrisome, however. As for updating, it is possible to update Tails to a never version, with all included software, using an ISO image. The image should be downloaded and verified on a "hot" system.

I use a similar method using a Raspberry Pi instead, for cold storage.
As long as you keep safe your seed you can always create the wallet in a newer version of Electrum or a future Tail version being sure that it will be working.

Raspberry Pi for cold storage? Interesting idea. Which OS do you use? I also have an old Raspberry Pi (model B) somewhere in my desk drawers.

Here is an old post of mine describing how it works:

https://bitcointalk.org/index.php?topic=2289365.msg24280376#msg24280376

Thanks. So you even deleted everything and kept the seed only? That's right, there is probably no reason to backup the wallet.

If you want to check your BTCs you can install the Electrum in your PC and instead installing your Master Public Key, to install your addresses one by one.
I've read (not 100% sure) that if your master public key and one of your private keys would be known, your wallet could be compromised.

Where I live I can't buy yet anything with BTC, so using them is not an issue at the time being.

TailsOS with electrum as cold storage is a perfect idea, I use it for my coins too. Furthermore, I like the "watch wallet" function which I use on my phone.

The only downsides are that up to now you can´t use segwit and if there is a newer version of tails, you will have to install the update manually, because there are no over the air updates.

Don't use tails because it has an old version of electrum that has trouble synching with servers. Use a debian live CD and install the latest electrum on it as per the instructions on electrum.org/#download i.e. using pip3.

Yes, that's very convenient.


Tails system is never going to be online anyway, so manual update is perfectly suitable.

The cold wallet will not be syncing with servers anyway, because the system will never be online. The only potential problem may be with wallet, seed or signature formats, not with server connections.

Also, the issue with networking with servers is generally fairly easy to fix.
And to confirm, along with the above posts of people who have used it with tails successfully, there should be no signature differences for legacy transactions and you should also be able to send coins to segwit addresses, just not sending a segwit transaction from your wallet.

Thanks, that's probably all I need. Maybe I'll want to move my coins to a new Segwit address in the future, but now it is not needed at all.

It should work fine with online version 3.x
I tried.

Well, considering that when you install tails you have to follow those steps, it is more or less time consuming:

- download the iso file
- install it on a USB drive
- boot from that USB drive
- install tails on the other USB stick
- format the first one

Compared to an over the air update which I imagine like that:

- Boot from your already existent tails
- press a button

Even if you have it not online except you need your money from cold storage, I would prefer over the air updates.

I'd recommend not using SegWit anyway yet at all in a wallet you're not going to spend from by any large rate as it doesn't save very much and there should be more to come so updating at every hard fork faced would just be to much of an arduous task to keep doing every hard fork (as there may be more to come and there's always segwit2x if that gets rescheduled.

Good. I installed it and tried to send a small sum to it. Watching-only wallets work, both under Linux and Android.

AFAIU, it can also be upgraded from a system running in a virtual machine, which is OK for me.

Thanks, I have a similar feeling and I'll follow this advice. It is not a spending wallet and will be used only when I decide to 'cash out' (partially) or need to move the coins to another cold wallet.

It seems I've found a bug or glitch in Electrum for Android. I've tried to create watching-only wallets several times. Two of them under Linux and one under Android work perfectly, but another one under Android shows the only transaction to the wallet as "Not verified" despite more than 90 confirmations.

What is the nature of that Android device? How full is it storage wise, how many transactions should it load?

Also, what is the operating system you're running, an old OS may not function as well as a new one (I had it on jellybean and it kept crashing).

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It's useful to know that in older versions, if you send a tansaction and the address is not in the offline sandboxed wallet, the transaction won't be able tobe signed unless you make the wallet aware of the new address (using a gap_limit command).

You can do this by doing either ^[1]:

or

Where n is the number of your addresses lus the nuber of addresses you want to make. If you have a lot of space, you may want to set this to something like 1000.

Google Nexus 5 with Android 6.0.1. More than 1GB free, 1 transaction only. After a few hours it finally showed the transaction as confirmed. I send another one and it displayed its confirmation progress normally.


In case if I send coins to some new addresses created in watching-only wallet and later want to spend them?

This is a known issue on the PC version. You just restart electrum to make it sync properly. I guess on android you would go to the app view (right most button at the bottom), close and then restart electrum. Alternatively changing the electrum server you are using sometimes does the job.


There have been bug fixes related to offline signing too since 2.7.9


The only fix is to install the latest version of electrum on tails. Simply changing servers doesn't do the job.

He can do "the only fix" once he connects to the Internet anyway at the point he wants to clear the entire wallet.

How drastic are the signing bugs exactly also? I was using an old version for quite a few months before updating.

Restarting did not help, but then it suddenly began to work normally. Well, it's a minor inconvenience.


I suppose it is possible to install the latest version to the Tails permanent storage and it should read the wallet properly, without the need to restore from the seed. Maybe it is better to do it right now.

Another question. Is it possible to export an incoming transaction from the watching-only wallet and import it to the cold wallet to make it show the correct amount without connecting to servers?

The watch only function of electrum on android seems slightly buggy for me too. I have ~30tx on the addresses I watch and it seems like electrum doesn´t remember that it received that the tx is already confirmed (it has to refresh it on each start). The more tx I get the longer it takes to refresh (show me that the tx is confirmed).

For my 30 tx which are displayed in my watch wallet, it takes ~ 15 seconds to load, maybe you got more tx and close before the app has finished loading.

I've encountered that glitch in a wallet with only one transaction.

Answering my own questions:


Yes, it works with the latest version (3.0.2), so i suppose there will be no difficulties accessing my coins later, when I need them.


No, it does not work. It seems that import is for signing only.

I've also tried to sign a message in cold wallet and then to verify it. No problems.