Cold Storage with Electrum Questions

[adaseb]

I would like to use Electrum instead of Bitaddress Paperwallets because I get a little paranoid not knowing if I will be able to ever withdraw any BTC from the private keys since I cannot test them prior before actual sweeping.

1) Just wondering if the guide shown here:
http://docs.electrum.org/en/latest/coldstorage.html

Is still up to date with the newer 2.7.12 version.

2) So as far as I can tell I don't need 2 computers, I just need another "offline" hard drive and I can simply switch back and forth. Correct?

3) I tried installing 2.7.12 on Ubuntu 16.04 however I ran into some errors when I tried to install Python 4, wondering if there is a step by step guide somewhere how to install Electrum properly on 16.04.

4) So as far as I can tell the "MASTER PUBLIC KEY" can be shown to anybody because it doesn't contain any seeds or private keys.

5) In case of offline computer/hard drive failure I should either PRINT the 12 worded seed or save on some USB key and keep offline forever? Or is there some file that I can save that contains the wallet backup of Electrum

6) The public keys generated by the 12 worded seeds is only good for the first 20 addresses. If I add any new addresses they won't be recoverable by the 12 worded seeds. So try to only use the same 20 addresses to prevent any future issues?

7) When I send a transaction, it automatically sends the change to some address that already belongs to me or is a new change address created and I need to backup the Electrum directory so in the future I can send the coins from that change address?

  8 ) Are operating systems interchangable between watch online addresses and offline signing addresses? I plan to use Ubuntu for Cold storage and Windows to broadcast the transactions.

9) So there is no way to reverse engineer my seed/private key when I broadcast my first transaction? A hacker can't look at my signed trans id and find a way to get my private key/seed from there?

I'll probably play around with some small BTC first by sending some to my Electrum created addresses, try to spend some, by signing the transaction offline. Do this a few times to make sure I can get the hang of it.

[ranochigo]

I would like to use Electrum instead of Bitaddress Paperwallets because I get a little paranoid not knowing if I will be able to ever withdraw any BTC from the private keys since I cannot test them prior before actual sweeping.

1) Just wondering if the guide shown here:
http://docs.electrum.org/en/latest/coldstorage.html

Is still up to date with the newer 2.7.12 version.

Yes.

2) So as far as I can tell I don't need 2 computers, I just need another "offline" hard drive and I can simply switch back and forth. Correct?

Yes. Remember to backup your seed, your harddrive might fail.

3) I tried installing 2.7.12 on Ubuntu 16.04 however I ran into some errors when I tried to install Python 4, wondering if there is a step by step guide somewhere how to install Electrum properly on 16.04.

On their download page: https://electrum.org/#download. I followed it and everything went fine.

And that is enough. What exact errors are there?

4) So as far as I can tell the "MASTER PUBLIC KEY" can be shown to anybody because it doesn't contain any seeds or private keys.

If you don't care about your privacy then go ahead. However, if you reveal both your master public key and one of your private key, an attacker can compute your master private key.[1]

5) In case of offline computer/hard drive failure I should either PRINT the 12 worded seed or save on some USB key and keep offline forever? Or is there some file that I can save that contains the wallet backup of Electrum

There is. Electrum saves the wallet files in a directory, go to File>Open and you should see where it is saved. I would recommend using the seed though.

6) The public keys generated by the 12 worded seeds is only good for the first 20 addresses. If I add any new addresses they won't be recoverable by the 12 worded seeds. So try to only use the same 20 addresses to prevent any future issues?

The xpub covers the entire range of addresses that can be generated by the seed. You just need the xpub derived from the seed. The seed and the xpub will generate the same address.

7) When I send a transaction, it automatically sends the change to some address that already belongs to me or is a new change address created and I need to backup the Electrum directory so in the future I can send the coins from that change address?

Already belongs to you. The change address is derived from your seed/xpriv/xpub.

 8 ) Are operating systems interchangable between watch online addresses and offline signing addresses? I plan to use Ubuntu for Cold storage and Windows to broadcast the transactions.

Yes. There is no difference between using windows to sign and linux to broadcast either.

9) So there is no way to reverse engineer my seed/private key when I broadcast my first transaction? A hacker can't look at my signed trans id and find a way to get my private key/seed from there?

I'll probably play around with some small BTC first by sending some to my Electrum created addresses, try to spend some, by signing the transaction offline. Do this a few times to make sure I can get the hang of it.

No, they can't. They can only reverse engineer your xpub and one of the private key as mentioned above.

[1] https://bitcointalk.org/index.php?topic=657205.0

[Cereberus]

I would like to use Electrum instead of Bitaddress Paperwallets because I get a little paranoid not knowing if I will be able to ever withdraw any BTC from the private keys since I cannot test them prior before actual sweeping.


3) I tried installing 2.7.12 on Ubuntu 16.04 however I ran into some errors when I tried to install Python 4, wondering if there is a step by step guide somewhere how to install Electrum properly on 16.04.

I want to talk about the step 3 as I had difficulties installing Python from the official electrum website "how to" in Linux Mint 18 latest version which is based on Ubuntu 16 I think so it's the same.

I followed these few guides. One is for installing Python version 3.x.x in a programming environment but who cares if you don't do programming , what I want to say is to be successful to install the Python so you can install Electrum after that.

1. http://tecadmin.net/install-python-3-4-on-ubuntu-and-linuxmint/#

2. https://www.digitalocean.com/community/tutorials/how-to-install-python-3-and-set-up-a-local-programming-environment-on-ubuntu-16-04

In the second guide focus only on the part of installing python, we are not interested in the programming part after that.

3. https://github.com/mhbashari/Install-Python3.4-on-Ubuntu-16.04

I was finally successful of installing and restoring my old seed of Electrum 2.5.4 in my new Electrum 2.7.12

Hope this helps.

[Coding Enthusiast]

I would like to use Electrum instead of Bitaddress Paperwallets because I get a little paranoid not knowing if I will be able to ever withdraw any BTC from the private keys since I cannot test them prior before actual sweeping.

https://bitcointalk.org/index.php?topic=339810.msg3647576#msg3647576
You can test it literary with any bitcoin wallet out there. Just remember to be on a live linux that doesn't save anything and check the signature of the downloaded file.

Just an addition to ranochigo comment
3)

Code:

sudo apt-get install python-qt4 python-pip
sudo pip install https://download.electrum.org/2.7.12/Electrum-2.7.12.tar.gz

7) You can also change this behavior by deselecting Use Change Address from Tools > Preference

8 ) You are broadcasting "bitcoin transactions" so technically you can even use a web service to push the signed transaction. Just open the .txn file that Electrum gives you with a text editing software like Notepad and you can see a JSON which looks like this:

Code:

{
    "hex": "010000000......", 
    "complete": false
}

Copy the hexadecimal in front of "hex": and paste it in a push service like https://blockchain.info/pushtx