Vitalk Buterin, Ethereum’s co-founder and all-’round crypto-genius,’ took to Twitter over the weekend to decry the increasing popularity of, what he termed, “ultra-heat-protective survive-a-nuclear-war, seed phrase storage devices.”

A seed phrase is a list of words which store all the information needed to recover the cryptocurrency in your hardware wallet, if it’s lost or stolen. But remembering the 12-word phrase—typically made up of random words—can be challenging. So most people either write it down or store it in a flash drive, or other storage device.

What triggered Buterin was the proliferation of seemingly indestructible storage devices—targeted those fearing a catastrophe such as fire, flooding, home invasion or nuclear war. He believes these devices are being developed at the cost of building better UX for other, more secure, methods of storage.

So what does he recommend exactly?

“My whole point is that these systems are not as secure [as] you think they are. It's still a single point of failure. I'm a huge evangelist for more secure systems, hence why I pump multisig wallets, vault contracts and social key recovery at every opportunity,” he tweeted.

Initially, Buterin’s recommendations were ”multisig,” which requires more than one trusted person to sign off on a transaction; vault contracts, which provide developers with a tool to make secure, automated payments to recipients; and social-key recovery, whereby one chooses three to five trusted contacts who can help recover one’s funds.

But it almost goes without saying that storing your key phrase in your brain—that is, memorizing it—ultimately emerged as Buterin’s primary recommendation followed by a nifty social-key recovery formula the math-maestro cooked up:

Buterin admitted that this method may not be straightforward enough for “non-math-nerds” and would require “special tools” for figuring out the equation. These, he suggested, are what we should be developing.

We asked our math tutor how to work it out. Basically, you assign each person a number, X. Be sure to tell them whether they are the 1x person 2x or 3x person. The number, X, has to be easily divisible, so it doesn't end up as a decimal. Then, you take the difference between any two people's numbers to work out the key number. Easy! Easy? More tools, please.