I remember hearing Google early in it's history had some sort of emergency back up codes that they encased in concrete to prevent them becoming a casual part of the process and they needed a jack hammer and a couple hours when the supposedly impossible happened after only a couple years.
> To their great dismay, the engineer in Australia could not open the safe because the combination was stored in the now-offline password manager.
Classic.
In my first job I worked on ATM software, and we had a big basement room full of ATMs for test purposes. The part the money is stored in is a modified safe, usually with a traditional dial lock. On the inside of one of them I saw the instructions on how to change the combination. The final instruction was: "Write down the combination and store it safely", then printed in bold: "Not inside the safe!"
> It took an additional hour for the team to realize that the green light on the smart card reader did not, in fact, indicate that the card had been inserted correctly. When the engineers flipped the card over, the service restarted and the outage ended.
There is a video from the lock pick lawyer where he receives a padlock in the mail with so much tape that it takes him whole minutes to unpack.
Concrete is nice, other options are piles of soil or brick in front of the door. There probably is a sweet spot where enough concrete slows down an excavator and enough bricks mixed in the soil slows down the shovel. Extra points if there is no place nearby to dump the rubble.
Probably one of those lost in translation or gradual exaggeration stories.
If you just wanted recovery keys that were secure from being used in an ordinary way you can use Shamir to split the key over a couple hard copies stored in safety deposit boxes a couple different locations.
