@aeischeid@mastodon.social we and my friend, we were also exchanging encrypted messages in 80ies in school. we had pretty impressive advancements, started first from sherlock's dancing man, then discovered mathias sandorf's grid and were trying to prepare good grids, then used pens that had custom invisible ink it it and we were keeping another chemistry that would allow to read such messages in the inner pocket of our school jackets.