Recent research highlights the use of letterlocking techniques

https://archive.ph/2kiw8

Is it correct that letterlocking is a technique that requires quantum technology to replicate in the digital realm? Strong crypto only works if you know with certainty your private key is still private.

video of how it's done: https://www.youtube.com/watch?v=dzPE1MCgXxo

This is the best resource IMO. I've sent a few letters using these techniques for fun. :)

It's just a paywalled article on letter locking.

https://en.m.wikipedia.org/wiki/Letterlocking

paywall :(

Was wondering WHY one’s most important secrets would need to be shared.