Manual authentication?

I'm concerned about deepfakes and would like to have a way to prove my identity when communicating with my family.

I've been thinking of creating index cards with a set of pre-shared keys for each family member and doing a simple challenge / response if we're ever unsure.

e.g., "Has my sister *reeeally* been in a horrible accident?? Tell me the code at position 23..."

One downside is that you'd have to invalidate codes as they're used.

Are there better …

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