Sunday, May 4, 2014

Laminated Paper Wallets

I just made a bunch of plastic-laminated paper wallets for my long-term bitcoin savings. I plan to keep these with my other valuable papers so they will be treated seriously in case I am no longer around. Here's what I did.

First, I went to the "Wallet Details" page of and entered my private key. I printed the page on my laser printer.

Then, I took a piece of black paper, cut it in half, and used half of it to cover the bottom half of the page where the private key is displayed.

I then laminated them together at my local Fexex Office location for $1.99 USD per page (they do not accept bitcoin). This sample is for the bitcoin address 1Fj3iqvDoFc74QyKpReW5m2eKdP2iauiNd, and it looks like this:

The resulting page is waterproof and should keep your data safe for a long time, though it obviously is not fireproof. When it comes time to spend the bitcoins, you can cut off the edge of the lamination on the bottom half of the page and it opens up to reveal the private key:

I did this with only moderate operational security. I didn't make an offline copy of and check its hash. My computer is connected to the internet (behind a firewall), so if a hacker has control of my computer they can get access to my private key. I have not worried about clearing my printer's memory, so perhaps someone who steals my printer will be able to access my private keys. Anyone who gets their hands on my paper wallet can spend my bitcoins; for more security use Shamir's Secret Sharing so that, say, 2 of 3 printed pages are required.

Sunday, January 5, 2014

Durable "fiat" paper wallets

I just discovered that my government makes and distributes fairly durable paper wallets suitable for use with Bitcoin. Here's how to use them.

First, select three of their paper tokens randomly:

Then, type in their unique serial numbers, concatenated together with a period in between, as the passphrase of a "brain wallet" on or These ones yield the bitcoin address 1M9kzNAURtUijDX9yPGh5UAmcEHvWT79VJ.

To ensure that your bitcoin private key contains sufficient entropy do not use new notes that just came from the bank. Instead select three different notes that you got as change from three different purchases. Then staple them together with a note that reminds you that these are not just some random bits of fiat.