The key is 64 characters? Even if that key is made out of decimal digits that works out to 212 bits. That seems quite excessive for a symmetrical key you are hoping to have a user deal with directly. It appears that the usability of this scheme could be significantly improved by simply using a shorter key.

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growse 6 days ago | parent [-]

What's the specific use case that benefits from a shorter key?

The only interaction I can ever see having with this key is putting it into and taking it out of my password manager....

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upofadown 6 days ago | parent [-]

The article specifically suggests writing the key down in a notebook. A single incorrect digit and the scheme fails much later in a way catastrophic to the user.

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whyever 6 days ago | parent [-]

Signal asks you to repeat the key immediately before even enabling backups. It cannot fail much later unless you modify the digit after the check.

	▲	upofadown 6 days ago \| parent [-]
		A longer key makes typing a bunch of characters back into the phone much less usable.