[mook]

I've seen https://github.com/cyphar/paperback before which basically does this, I believe. I haven't used it in the context of letting other people recover things though.

[vorgol]

Visual cryptography is really cool. Shamir and Naor came up with an algorithm in the 90s: https://en.wikipedia.org/wiki/Visual_cryptography#Example

Basically hand out transparencies to n people, and they all have to overlap to see the picture. It's like magic when you're playing with them.