Materials

That's enough rambling from me about self-custody, let's get on with the article. The following describes how to verify the latest version of the ColdCard firmware is being used; how to generate a new seed with 256 bits of entropy using a 6-sided dice; how to verify that the ColdCard is actually deriving seed words from the user's unique dice rolls; how to backup that seed phrase into stainless steel washers using the Blockmit 3D printed jig; and finally, stress testing the backup. To get started, there are few necessities. If you're following along at home, gather the following items:

  1. Paper Notebook.
  2. Writing Utensil.
  3. Hammer.
  4. Six-sided dice, preferably a balanced casino dice.
  5. ColdCard with cable, power adaptor, & battery.
  6. Blockmit 3D Printed Jig. Available at CryptoCloaks.com
  7. Letter & Number Stamp Set. 3mm (1/8").
  8. Stainless Steel Washers. 8mm I.D. x 24mm O.D. x 2mm thick.
  9. Stainless Steel Wingnuts. M8-1.25
  10. Stainless Steel Bolts. M8-1.25 x 60mm.

I already had a notebook, pen, hammer, dice, and ColdCard at home so I spent about $65.00 gathering the other materials, which was enough to make four of these backups which come out to less than $17.00 each.