Making my own phrase backup washers with laser…

Just did an experiment and I’m going to make my own backup washers using my laser and Enduramark (like Cermark) laser marking spray.

It’s extremely durable and basically fireproof.

I won’t get into the nitty-gritty on how I’m keeping this secure (for brevity) but it’s roughly like this:

From the BIP-39 I randomly (with a truly random randomized) picked 96 words.

I transfer those to a non-internet connected computer and randomly replace 24 of them with my words. Then still offline I lasered them onto washers. I obviously won’t laser all 96 but they are all in the job in case someone gets a log from my laser (like if it phones home).

This results in about 145 bits of entropy. So even if someone knew the 96 words, it would be pretty darn hard to do anything with them.