early end to end encapsulation

letterlocking was used as a tamper-evident closing of a letter by using folds, cuts and glues to make it difficult to snoop undetected

Not really encryption, but still a lot more work than GPG encrypting something

https://www.bbc.com/future/article/20210616-how-the-forgotten-tricks-of-letterlocking-shaped-history?utm_source=pocket-newtab

#PaperSec #LetterLocking