1

I'm considering making cold paper wallets (for multiple cryptocurrencies) for offline storage in a safe deposit box. Before accessing the safe deposit box, my identity is checked and I must show my key, so I consider storing the paper wallets non-encrypted.

They are a lot of tutorials on how to generate a wallet on an offline computer, but I'm searching for an efficient way of transferring the wallets to the paper.

Here are the options I have considered, and I would like your opinion.

Handwriting

In a technical point of view, handwriting the wallet key seems secure but tedious. I'm not very confident about reading my own handwriting in ten years, especially in base56 , not talking about my children reading it.

Low-cost laser printer

Buying a $60 printer that should be supported by the offline computer. I think that kind of offline printer will be unlikely to store my private keys and even more unlikely to transmit them.

typewriter

Buying a second hand typewriter and typing the key on it. Seems pretty secure and relatively easy, if the key can't be extracted from the ribbon.

Label printer

Label printers can probably work without a driver, just by echoing the key through the serial port, but thermal paper won't last enough, thermal transfer can be read on the ribbon and matrix printers are expensive.

Embossing label maker

I'm pretty sure that this one can't be hacked and can be read by anyone in thirty years, but they don't have upper and lowercase required for base56. Writing the key in hexadecimal can be a solution.

1

You can use BIP 38 encryption to encrypt your private key and then just print out your private key normally. BIP 38 will encrypt the private key using AES with a passphrase of your choice (so make sure that it is a secure one) and encode it using Base58 Check Encoding so you will get a string that is your encrypted private key. Because it is encrypted, you can print it out normally without risking the private key being revealed as the printer and any devices on the network will only see the encrypted string and not the actual private key.

The only caveat is that if you forget your passphrase, you lose the private key. One way around that would be to write your password on the printout.

  • Seems a good idea, but I think handwriting a good passphrase is as difficult as handwriting the full wallet key. – pim Oct 23 '17 at 14:31
1

if you are handling large amounts of value and dont mind spending a bit more than expected, you can buy literally any printer you like.

just make the keys offline, print them offline, then properly exterminate the printer (and maybe the computer as well). I would use fire. lots of fire.

extra points if you make them while enclosed in a faradays cage using a battery for your energy source.

if you plan for the long-term, consider how well paper, die and similar age. laminating the paper might be a good idea.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.