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For a long time, now, Leo and I have been listening to audio books of long Fantasy and Steam Punk series, and at some point I’ll write a post — or probably several — about our responses to these, as there’s a lot to say. But occasionally we are able to make a contained and useful lesson out of some tidbit in these series. For example, the wonderful Leviathan series by Scott Westerfeld offers many opportunities ranging from discussion of evolutionary theory to the inventions of Nikola Tesla.

One of the ongoing issues that Leo and I discuss around these various series is the difference between fantasy and science fiction (or steam punk, which is what we tend toward). This is, of course, not a simple question, and the answer is probably as philosophical as it is problematic, so I’m not going to offer any deep theory of it here. But only of the things that is more-or-less clear is that in fantasy you can just make things up, that have no bearing at all to possible physical reality, whereas in SciFi/steam punk, there is generally some plausible way in which at least most of the things that play a role in the story could have some plausible reality in our real universe. So, in fantasy you find magic, whereas in SciFi you get machines. Whether the machines are really plausible is debatable — sometimes they’re time machines, for example! But at least there’s no explicit magic in SciFi. SciFi sort of has to follow the rules, whereas fantasy came just make up magic. In fact, this is one of the problems with fantasy: If you can make up random magic, why can’t you just make up magic that solves whatever problem you have. Fantasy writers end up creating endless random constraints on their magic in order to keep the story interesting. (“You can only use the magical Time Turner twice on Tuesdays between the hours of 3 and 4 pm when the moon is blue.” … or whatever …)

The opposite direction is less constrained; You often find steam-punky-quasi-machines in fantasy: Doors with special complex locks seem to be a favorite, with special keys scattered all about. The series that we’re listening to at the moment is the extremely long, but wonderfully written Septimus Heap series, by Annie Sage (hereafter SH).

There are many interesting things about this series (and about all of the series that we’ve been reading and/or hearing), but I just want to draw out two small details in SH that struck me as particularly interesting and funny, in a somewhat STEM-educational sense.

Hyper-Literal AI Self-Driving Sled Gone Wrong

The climax of the 5th book in the SH series, Syren, turns on a bunch of under-sea tunnels, called “ice tunnels”. It’s not giving away too much to tell you that in order for our heroes to get through these tunnels fast, they utilize a magical sled, which they can call remotely, and which is some sort of AI that they can tell where to go within the ice tunnels. At one point our heroes call the sled, which shows up (just in time, of course!) and upon climbing aboard, they tell the sled to “Head for the nearest hatch!” The sled takes off at a shot, but in the wrong direction! Too late they realize that what they should have said is: “Head for the nearest hatch in the castle!” The literally nearest hatch is in the opposite direction!

Public Key Encryption Saves (actually nearly loses) the Kingdom to the Dark Domain

The resolution 6th book of the SH series, Darke, turns on the decoding of a spell that will save everyone from some sort of magical evil, called the “Dark Domain”. The spell is protected by a complicated split key book cipher, with a few interesting properties. First, interesting property of the cipher is that each part lives on a circular disc — something akin to a DVD, but where you can read the “bits” off it with a strong magnifying glass. The circularity of the discs introduces an interesting problem, which they make a bit of in the story, which is that you don’t know where to start on a circular cipher! You could use the grammar of the language, or try all 49 (in this case) starting points, but Sage pulls out plausible escape clause that these are many hundred year old spells, and also that if you get it wrong you could do more harm than good. Hilarity ensues, and, of course, good triumphs over evil at the last possible moment.

(Another slightly funny aspect of this situation — if you’re 8 years old! — is that one of the halves of the split key had been eaten by one of the bad guys. The heroes had to get him to throw it up, and then utilize the disgust-covered disc! I guess it could have been worse! 💩 )

All this is very interesting (or perhaps not), but the point for the present is that Leo and I were able to use this imaginary cipher as a jumping off point for discussion of public key encryption, which is also a split key cipher, the details of which basically followed this excellent Numberphile video. (Numberphile, by the way, is a terrific video series on math … or as the Brits call it, “Maths”.)