Matt Peperell's Blog

Lamenting the downfall of rot13

Written: 10 Dec 2021 (Index by date)

Tags: tech  nostalgia  (Index by tag)

When I first gained access to the Internet in the mid 90s, the world was a very different place. The web was still in its infancy. Usenet was still very popular. Online culture was very much focussed on sharing of information rather than the skew towards collection of data that seems to proliferate today.

One of the things I remember is ROT13 - a simple way that text would be hidden, but done so in an intentionally simple way. It was simple enough that with a little practice one could even decode it by eye, though it was rare for people to actually do that; typically email clients and newsclients would have ROT13 functionality built in.

It worked as follows: All non-letter characters (such as punctuation, spaces, new lines) would be unchanged. But every letter would be advanced 13 spaces in the alphabet, remaining as upper case or lower case, depending on what they were originally.

The real elegance of ROT13 is that the same calculation can be used to both “encode” and “decode” the text. In other words, there’s no need to know whether a text segment is coded or in plaintext before applying the transformation. It was simple to implement.

Some examples: A would become N, B would become O, C would become P etc, but also note that N would become A (since there isn’t a letter after Z). The same thing would apply for the lower case letters.

Click on this text to see the effect. Guvf grkg jnf uvqqra ohg vf abj erirnyrq.

Here’s another example. The English alphabet in both upper case and lower case:

ABCDE FGHIJ KLMNO PQRST UVWXYZ abcde fghij klmno pqrst uvwxyz

Why was such a thing used? The common use cases were

It seems as though ROT13 has fallen into disuse these days. It also never really became widely used on the web. I’m not sure why either of these might be so, but I still have a soft spot for ROT13. One possibility that as Javascript became more widely adopted on the web, designers used more aesthetically pleasing techniques such as blurring or black bars, or perhaps having the solution behind second page load.

I’m not trying to make a point here. Instead, I merely felt indulging in a little nostalgia.

I’ll finish with a joke: When is a car no longer a car?

Jura vg gheaf vagb n fvqr fgerrg.
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