Paper Wallets : Do you somehow validate that the pk QR work b4 using?

mgio

hero member

Activity: 546

Merit: 500

Quote from: Abdussamad on May 31, 2013, 12:53:30 PM

Up to 30% of the QR code can be damaged and the key will still be read. This is a feature built into QR codes:

http://www.qrstuff.com/blog/2011/12/14/qr-code-error-correction

Similarly a key stored in Wallet Import Format has a checksum that ensures you can't import a mistyped key. This won't save you if the key is misprinted or damaged, though. It just ensures that any key you import is a valid one.

So as long as you print the QR code of the private key you should be ok.

Another thing you can do is spread out your coins in small amounts among multiple private keys. Say BTC 0.05 per key. That way any damage to one or two keys will limit your losses to a fraction of a bitcoin.

So wait, you are saying create 20 QR codes for each bitcoin you own??!

johnniewalker

legendary

Activity: 896

Merit: 1000

Quote from: orz.dk on May 31, 2013, 11:57:04 AM

Hey,

I'm about to move some funds to a paper wallet, but then I got spooked, thinking that the possibility of my printer making an invisible, but damaging print error in the private key QR, could exist. Ok, i could then type the key, but the pk font (at least in the default template from bitaddress.org) is tiny and smudge prone on a less than great printer, and it would be a bit unnerving.

Do you personally somehow validate that the pk QR's work before putting btc on pw address ?
Can someone recommend a trusted, offline paper wallet thingy that prints the pk a bit larger?
Does anyone use special paper ? (photo paper/settings even??)

I could just scan the pk with QR droid on my phone to verify, but then it's not truly 100% cold anymore.

Thanks for input !

/orz.dk

You can check it with your phone. Otherwise you're bordering on paranoia. I always check mine.
I have printed QR codes as small as .6'' x .6'' (to reload Casascius coin) and it works fine. I would stay away from glossy photo paper...has the highest tendency to smudge.

Abdussamad

legendary

Activity: 3710

Merit: 1586

Aha and there's even more. You can do an M of N setup. N private keys/shares out of which you need M to spend your coins. Different ways of doing this:

   - Send to a multi-sig address. All private keys will be required: https://people.xiph.org/~greg/escrowexample.txt

    - Secret sharing: http://bitcoininformant.com/2012/06/update-splitting-bitcoin-secrets/
      https://bitcointalksearch.org/topic/paper-wallet-20-using-shamirs-secret-sharing-scheme-idea-148809

   - Contracts: https://en.bitcoin.it/wiki/Contracts

   - Edit: Using Armory: https://bitcointalksearch.org/topic/ann-m-of-n-fragmented-backups-now-in-armory-command-line-only-149820

Some clients support offline wallets so you don't have to mess with paper wallets:

https://bitcoinarmory.com/using-offline-wallets-in-armory/
http://electrum.org/offline_wallets.html

ThatDGuy

hero member

Activity: 728

Merit: 500

Quote from: Abdussamad on May 31, 2013, 12:53:30 PM

Another thing you can do is spread out your coins in small amounts among multiple private keys. Say BTC 0.05 per key. That way any damage to one or two keys will limit your losses to a fraction of a bitcoin.

Good tips. Also make sure they are stored in more than one secure, fireproof location.

Abdussamad

legendary

Activity: 3710

Merit: 1586

Up to 30% of the QR code can be damaged and the key will still be read. This is a feature built into QR codes:

http://www.qrstuff.com/blog/2011/12/14/qr-code-error-correction

Similarly a key stored in Wallet Import Format has a checksum that ensures you can't import a mistyped key. This won't save you if the key is misprinted or damaged, though. It just ensures that any key you import is a valid one.

So as long as you print the QR code of the private key you should be ok.

Another thing you can do is spread out your coins in small amounts among multiple private keys. Say BTC 0.05 per key. That way any damage to one or two keys will limit your losses to a fraction of a bitcoin.

orz.dk

newbie

Activity: 30

Merit: 0

Hey,

I'm about to move some funds to a paper wallet, but then I got spooked, thinking that the possibility of my printer making an invisible, but damaging print error in the private key QR, could exist. Ok, i could then type the key, but the pk font (at least in the default template from bitaddress.org) is tiny and smudge prone on a less than great printer, and it would be a bit unnerving.

Do you personally somehow validate that the pk QR's work before putting btc on pw address ?
Can someone recommend a trusted, offline paper wallet thingy that prints the pk a bit larger?
Does anyone use special paper ? (photo paper/settings even??)

I could just scan the pk with QR droid on my phone to verify, but then it's not truly 100% cold anymore.

Thanks for input !

/orz.dk

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