The clever folds that kept letters secret | Hacker News Reader

The clever folds that kept letters secret

bbc.com

33 pointsrobalicious10 comments

Open articleView on HN

Previously on HN:

https://news.ycombinator.com/item?id=26532134

https://news.ycombinator.com/item?id=26555153

https://news.ycombinator.com/item?id=18420924

https://news.ycombinator.com/item?id=26338673

https://news.ycombinator.com/item?id=26327888

After watching the video I do not understand what prevents anybody from reversing the strip through the hole after drying it.

It doesn’t prevent observation - it provides evidence that it was observed. Likely with a ton of effort and careful application of steam, etc you could defeat it - but it’s more designed to prevent casual snooping.

So don’t think PGP encrypted but think a URL that records who views it.

Why is it difficult to undo, then redo? Obviously one need to be careful (twice) but that's all

The key is the adhesive which means you have to tear or otherwise undo it before you can unfold it.

I suspect that much of it was simply “how can we fold the letter” taken to extremes as a form of individual expression.

Perhaps wetting and mashing it down changes its shape and strength so it's too delicate to reverse.

I picture it like being more complex than re-folding a street map. It seems a good lot of people mess that up, and it's easy to tell it's happened because some of the folds go the wrong way, and sometimes there are new folds and "puffy" edges that don't belong there.

Just like ironing, where sometimes you see an erroneous V-shaped pleat running down the front of an otherwise impeccable pair of dress pants.

That's a lot of faith in the strength of a small strip of paper, I'd probably rip the thing several times just trying to make it like the video

Did they have stronger paper back then?

I assume they did but costs were associated - considering they were avoiding envelopes.

Making paper was a lot harder back then and they didn't have the machinery to create the uniform thin paper we have now. So you ended up with a thicker paper with more variance.

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