Cold Storage without a (secure) printer

If you don't have access to a secure printer, or a printer at all, but still want to have a cold storage paper wallet, this how-to is for you.

A printer is considered insecure, if it's connected to a network or if it stores the print jobs in some internal memory. A general rule of thumb is, the dumber the printer is, the better. So a $30 ink jet is probably a better choice to create paper wallets, than a $300 all-in-one machine that receive e-mails, send faxes, etc.

(Side note: If you use an inkjet printer, it's prudent to laminate the paper wallets or protect them in some other way from moisture.)

What stuff you will need:

What knowledge you will need:

What will happen: You will create a Linux system on USB-drive-A. Then you will place all the tools you need to create a paper wallet on USB-drive-B. Then you will disconnect your computer from the network. Then you will start your computer from USB-drive-A into Linux. And then finally you will use the tools to create a paper wallet.

Preparing the Linux system on USB-drive-A

First you have to download an image of a Linux distribution. Ubuntu or LinuxMint is generally a good choice, being compatible with most computer hardware. You probably will need the 64-bit version, aka amd64-version.

Once you've downloaded it, you can start creating the Linux system on USB-drive-A.

To create the Linux system on USB-drive-A, use the tool UNetbootin.

  1. Just plug USB-drive-A into your computer
  2. open UNetbootin
  3. select "Diskimage" and chose the Linux distribution image you downloaded earlier
  4. choose your USB-drive-A as the drive to install to
  5. and then start the process.
Once it's finished, you can unplug USB-drive-A.

Preparing the tools you need to create the paper wallet

Go to https://iancoleman.io/bip39/ and save the page to USB-drive-B. I will refer to this site as BIP39-site now.

Then got to https://keybase.io/warp/ and save the site to USB-drive-B.

Now unplug USB-drive-B, remove all network cables from your computer.

Restart the computer from USB-drive-A.

Once it started up, plug USB-drive-B in again. Open the BIP39-site and create a mnemonic seed of at least 12 words. I just created this 15 word seed

pistol woman turtle rug sand okay field glad check divide concert gasp budget old casino

Write it down on the piece of paper you prepared. This is the key to the kingdom. This effectively is your cold storage paper wallet. Now all we have to do, is create actual bitcoin-keys and bitcoin-addresses from it.

For that open the offline copy of WarpWallet.

Enter the seed words you wrote down before, all lower case, with a single space between the words. And after the last word, append -1. Then click on "Generate".

So the seed I created before would now look like this:

pistol woman turtle rug sand okay field glad check divide concert gasp budget old casino-1

and it would produce the address

13AEhBHeVDKr7bRygbuSFiGb7t9ATj4z8p
and the key
5HtALTbt4L5SgMrojfguw2oAkqS83UDHzSd7dzHmZargXF2y2df.

Open up an empty text-file and copy and paste that address, not the key, into it. Save it to USB-drive-B.

Repeat with appending -2, -3,... until you have enough addresses. Save them all to the text-file on USB-drive-B.

Ubuntu and LinuxMint even come with LibreOffice, so you can paste them into a Writer-Document and either download LibreOffice or OpenOffice for your main-system, or save the document containing your addresses as a Word-Document.

That's pretty much it. You can watch the addresses using sites like https://blockchain.info from your online system.

Secure the seed that's on the paper, make an off-site backup, like in a bank safe deposit box, or in an envelope at your grandma's house. You can also print out this page, or save it somewhere, to make sure you can create the private keys, if you want to access your bitcoins.

To access your bitcoins, recreate the private keys by following exactly the same steps as above (minus the seed creation of course). Then you can import the individual private keys into Mycelium (Android), BitWallet (iOS), do your business and send the remaining bitcoin balance back to a yet unused address, like the -2 address if you now used the -1 address and key.


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