Re: A few questions because I don't understand how BTC works it doesn't make any s.

Thank you
So concretely: how can I save a few thousands $ worth of BTC without having to rely on an online service trust?

You'd use a wallet like electrum and bitcoin core. In both of those cases it's highly unlikely you'll get scammed by their developers and you do own the private keys.

Quote from: alexlouismorlevat on November 08, 2017, 05:02:40 PM

Should I save the private keys? OR the seed "big number"? OR the seed list of words on a piece of paper?
What software to use?

The seed is all that is needed. If you use a bip39 wallet you may also get a master private key that yoy can also store in case of transcription/data loss errors.

Quote from: alexlouismorlevat on November 08, 2017, 05:02:40 PM

Let's say I want to use 2 pieces of paper that will be in 2 locations. What software or what to use to generate the words that I'll write on those pieces of paper? I can't use Electrum because it was said that only Electrum software can generate the "big number" from the list of words. So if Electrum disappeared my piece of paper would be then useless because I could not use any software to convert the list of words into the big number and then into the private keys.

Electrum is a piece of software, it cannot disappear. There is no master deactivation switch in the developers basements. As long as you keep a copy of your seed, you're good. Should electrum not be accessible, there are achieved versions of it stored. There is also the connectivity issue as it is an spv Waller and is a bit irregular compared to regular nodes. In this case, you can import your seeds into bitcoin core.

Quote from: alexlouismorlevat on November 08, 2017, 05:02:40 PM

And when I open Electrum it asks me to select a file. What is this file?

Did you download it from electrum.org? If so, just input a random name if it already says "Default_Wallet". Keep it that way for now.

Quote from: alexlouismorlevat on November 08, 2017, 05:02:40 PM

My goal would be to have those few words on paper and only this paper is needed to access my BTC.
And this paper would be the ONLY way to access my BTC and being able to send them to someone, or to check the balance.
Would that work?
I just don't want any technical hack to be possible, except finding the list of word and knowing what is it, etc...

Yes that would work. Once your words are written down and stored safely you should be good to go. Make a couple of copies of the seed though.

When you say "make a couple of copies of the seed". Do you mean write down the list of words on several pieces of papers placed in different locations?
About the file that is created by Electrum. Do I have to save this file? Or delete it? Does it contain the keys? Or anything else?

Yes make multiple copies in multie places for good security.

Do what you want with the file. The seed contains everything and is all you need.
You could place it on a pendrive as an extra backup or just delete it.
As a note. For maximum security store it on a separate disk when creating it and then destroy/rewrite to the dusk multiple times until it is completely full to ensure everything is completely deleted (a vhd file will do this for you).

Does the not encrypted file generated by Electrum is enough, by itself, to access the wallet and use the money?
So I could put this file on a simple usb key to have another form of backup? (edit: this idea is useless I just have to create a text file with the few words' seed and put that on the usb key).
I could also put the file into an encrypted container created with VeraCrypt or whatever?

Edit: I don't find a way to open a file previously created.
Also, why does it always have to create such a file.
Really, what is this file and what is inside?
If I just want to enter my seed and manage my money, I don't want to create a file that I have to delete each and every time for safety reasons??

If you're on Windows, you could try to find the folder downloads are stored in when you click "open" instead of "save" as I believe that wipes every time you restart the computer. Simply make a shortcut to that folder and put electrum in it and run if from there. As a warning. You'll have to test this works due to Windows settings changing slightly. Also could try booting live Linux from a usb.
Otherwise, there's no way to stop the file from being made.
And you got it that you can just copy-paste the seed to a usb. I think there should be a built in encryption on your computer to encrypt an entire partition (definitely NTFS has one).