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by zepolen 3179 days ago
The best way to store data longterm on hardware is a QR code on a metal punch card, with holes for the black parts.

That would probably be the most robust method to withstand fire, rust and anything else.

You'd need access to a laser metal cutting machine for that though - or drill each hole one by one heh.
1 comments
IvanAnishchuk 3172 days ago
What about actual punch cards? Maybe not the most efficient given the lack of equipment but should not be harder to print or punch than QR. And standards were around for much longer than QR or DM so you can be sure to find some designs online or in a library if you lose all of of your equipment in 10-50 years (and they can always be scanned or read by eye if everything else fails). I'm looking for a simple design for a RS232 puncher, preferably one that would support some non-biodegradable plastic cards (they say PET bottles do not degrade in centuries, ain't that a perfect backup material?) But even paper cards should be more durable than anything printed on laser printer.

Using IBM 80-column cards you'd need just about 10 cards to store a 4096-bit key with three subkeys in binary mode. More if using char mode (might be preferred if you have to type them using keyboard). The key can be condensed for backup if needed. OTP and/or Shamir's method could be added to the mix to improve security, increasing the number of cards required, but even without Shamir you can split the deck in half and store in different places.

Longer, possibly foldable, punch tape is yet another option. If it has the same width as IBM 80-column cards then most of DYI equipment designed for the latter can still be used. It can't be metal though, only paper or plastic.

A bit of obscurity helps too, it's not like a deck of cards screams "this is an important secret" or possible attackers have card scanners with them when they invade your backup facility (although they can make photos and decipher them later so it's not real protection, just a small bonus.)

Now, how would we solve a problem of rubber-hose cryptoanalysis with it?

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