Paper wallet

Storing Crypto-currency in a paper wallet is one of the simplest ways to hold your savings securely, but you should follow some important steps to be sure that you can truly be confident in its security. A paper wallet is a way of keeping your assets safe by having the only way to access them written on a piece of paper so that they're safe against hackers, theft or mechanical failure.

There is a protocol called BIP-39 which many wallets such as Electrum, Coinomi or Exodus use so that all the addresses they use along with their private keys are generated from single seed phrase. This seed can generate any number of addresses for assets across most different types of cryptos. This means that a single phrase can act as a backup for many different addresses and cryptos, and since many different wallets support the protocol, the same backup phrase can be imported into any of them. This is a very good foundation for a paper wallet.

Coinomi have released an open source standalone BIP-39 seed generator that allows you to generate BIP-39 phrases and to see the addresses associated with the phrases. Just save the tool (by right-clicking the "raw" button and selecting "save link as") and the run it in you browser. Select the number of words (usually 12 for most wallets) and then you can select different coins and check their addresses from the bottom of the page. The image to the right shows the relevant fields in the Coinomi tool page that appear after you click the "generate button", first is the backup phrase, second is the number of words which is usually 12, third is the type of coin you want to see the addresses for, and last is the first address in the list. You can change the coin setting to get the addresses of different coins without the phrase changing. Alternatively you could enter an existing phrase to see more different addresses associated with it.

To make a really good paper wallet that you can be confident storing your savings in you should do this generation phase offline, and also you should do it from a trust-worthy (open source) operating system that has itself never been online either, so you can be sure there is definitely no malware installed in the system such as backdoors or keyloggers. This can be done by disconnecting your computer from the net and rebooting it into a clean Linux operating system on a USB stick, then running the BIP-39 tool, writing down a newly generated phrase and saving the relevant addresses on the USB stick.

Here's the exact steps that can be taken to make a paper wallet with the Coinomi tool. Here I've also included the Exodus wallet in the procedure, but this is optional. It's just useful if you use Exodus, because Exodus has a feature that allows you to open a wallet in "read-only" view so you can check on your balances or asset addresses without exposing the private keys. If you use only the Coinomi tools then you'll need to look directly on the blockchain to see the state if your assets, but this can be quite time-consuming if the wallet contains a few different types of coins.

What you'll need

• One USB stick with a bootable Linux such as Linux Mint on it.
• Another USB stick with the latest Exodus for Linux on it, and also this standalone BIP-39 seed generator (to save it, right-click the "Raw" button and select "save link as").
• A pen and paper :-)

The procedure

• Disconnect your computer from the network and reboot into the live Linux OS on the USB stick.
• Insert the other USB stick and run both Exodus and the BIP-39 seed generator, and also open a text editor.
• In the seed generator page, select 12 for the number of words and click "Generate", then write down the resulting twelve words - this is your paper wallet, make two copies and keep them both in safe secure places.
• Open a text editor and copy/paste all the addresses for coins you're interested in
• Save the text containing all your addresses onto your USB stick
• Now open Exodus and click "restore from 12 word phrase", it will then restart and allow you to paste the twelve words in that you copied in the previous step.
• Wait for the recovery to complete which may take about five minutes (even though we're offline, it still takes a while since it keeps trying to connect).
• Select "wallet", go to all the asset types you care about and look at their receive addresses, you'll see they're the same as the ones you got from the Coinomi tool
• Open the developer menu (CTRL+SHIFT+D) and select "Export Safe Report Data". The Safe Report is a read-only backup you can use to check on your savings safely
• Save the Safe Report from the exports folder on the desktop to your USB stick.
• Remove the bootable USB, reboot into your normal OS and reconnect the net.
• That's it! You can now send assets to the addresses you noted down.

Accessing the assets

To check the balances of the coins in a safe read-only way you can run Exodus and import the safe-report zip file you exported, note that this will over-right any existing data in Exodus. The safe report allows you to easily keep track of the balances of all the assets in your paper wallet, and even to obtain public addresses of other assets in the same wallet you may wish to send coins to that you didn't initially make a note of.

To spend the coins, you'll need to run Exodus, or any other BIP-39 compatible wallet like Coinomi, and recover from the twelve word phrase - but note that you would have then compromised the security of your paper wallet, so once you do this it would be best to create another paper wallet and send the remaining funds to it.