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  • Writer's pictureeconoalchemist

Where do seed backups go when they die?

An exploration into the various seed destruction methods on the heavy duty, 2mm, 304 stainless steel @bitcoinbackup from @Coinkite.

2020-06-16: While Canadian authorities continued their crusade to ban, not only BMG .50 caliber rifles, but also the great outdoors, resourceful citizen, @nvk, turns to Twitter and posses the question:

“Who's willing to take @bitcoinbackup to the range for a multiple caliber test on video, releasing us from any liability?”

I knew right away that it was my duty as a freedom loving Bitcoiner to step up to the challenge and help a friend in need. At the time, I wasn't sure how I would do it, where I would find a BMG, or if I would spend the rest of my days trying to outrun the Royal Canadian Mounted Police. But a couple of DM's later and an email to CoinKite support with shipping instructions and the wheels were in motion.

But why?

SeedPlates offer a robust method for securing Bitcoin mnemonic phrases. Usually, a wallet will produce 12 or 24 words that the user needs to keep safe. Taking a picture of the words, typing the words in a document, scanning the words into a .pdf, or digitizing the words in any way is frowned upon as this widens the attack surface considerably. Writing the words down on paper with ink is recommended but this too has drawbacks like fire or water damage. Steel plates can be used to protect against digital interception and environmental harm. With these particular seed plates, the English alphabet runs along the X-axis and 4-column wide sections run along the Y-axis. The user only needs to stamp the first four letters of each word as that is all that is needed for a BIP39 compatible wallet to regenerate, no two words on the BIP39 word list have the same four letters.

Suppose for moment that you drained all your bitcoin from an old wallet. Is it safe to just throw the old backup in the trash? If you had KYC bitcoin in that wallet, then some of those addresses are tied to your name. How would you feel if someone signed a message from an address tied to your name?

Properly destroying your seeds is important for preserving privacy even after the wallet is no longer used.

Here is multiple caliber test footage of four @bitcoinbackup plates from @Coinkite starting with .22 caliber:

The .22 wasn't quite destructive enough. The bullets didn't even pierce the plates. That says a lot for the plates! In this next video we stepped it up to 9mm. Unfortunately, we only had 8 bullets and I missed 7-1/2 times. We even drove into the nearest town trying to get more 9mm ammo but the local sporting goods dealer made it sound as though the whole state of Colorado was fresh out.

The 9mm seems like it would have been effective enough if the gun hadn't been bent and caused me to miss so many times. But we'll just have to imagine what the 9mm damage would have been with a direct hit. I think it would have pierced the plates. Next, we stepped it up to 7.62x39 with an SKS rifle.

The 7.62x39 was certainly sufficient for piercing the plate and removing enough material to conceal what was stamped into the plate with enough direct hits. But let's see what a .44 magnum can do, just for good measure ;)

The .44 magnum was the most destructive of the calibers we tested. A friend of a friend who was supposed to have the .50 cal bailed out at the last minute. We were going to go to Colorado Springs and rent a .50 cal from Dragon Man but they wouldn't let us bring steel targets onto the range. Shooting the plates was more efficient than drilling holes, cutting with a saw, or melting with a torch. As demonstrated in this video:

With the drill you have to make too many holes to randomize the pattern. With the saw you have too many pieces that you have to distribute to different geographic locations so the plate can't be put back together. The torch leaves no trace, but it's not for amateurs.

I hope you found this thought provoking & useful. Thank you to @nvk & @Coinkite for giving us the plates for our research! And special credit goes to my buddy @waleehooha for supplying the cameras & editing all the video footage! If you want some videos made he takes bitcoin.

Here are links to the hi-def videos:


Thanks for reading! I hope you give some consideration to how you handle robust seed backups after you're finished with them.

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This article is available on Twitter as a thread here.



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