UV Ink?
Put a Bitlocker (or similar) password on that
Speaking of Passwords, another thing you can do is, for example, a 12 word pass phrase, store 11 of them on your data storage a memorise one. This one doesn’t have to be the first or last but as long as you know the word and where it belongs.
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Or alpha numerics, or a number equation that you know the formula to, or a cypher…you have many options, you just need to know which one(s) suits you better