Pondering encryption within the medieval setting?

I'm writing an Ars blog post at the moment about magic which can be used to encrypt and decrypt messages or texts.

Along with everything else it will hopefully cover some historic refs for historic encryption, some basic guidelines, and sample spells. I noted the Cipher of Trianoma (in HoH:TL p20-21) injects simple ciphers and the crypto concepts into the Order, but as I thought more about the magic system for Ars the more I have conflicting thoughts on how this would be understood in the magical paradigm.

The key concern is how magic would actually process and understand encrypted material. eg.

  • How does magic view an encrypted item? Can I cast a spell to decrypt a message written by the Cipher of Trianoma? Why is it different from translating from one language to another?
  • How would magic apply itself to the problems of brute force analysis to break codes?

Magic has the ability to translate automatically between languages, or translate meaning between men and beasts. By comparison it seems trivial to decrypt a text. The meaning and context is the same, it is just the language which obfuscates the understanding.

My initial stance is that the intent and act of hiding the message is something that magic has more difficulty in understanding that a letter written openly. This would make it harder, but not impossible. I also wish to describe some of the different styles and complexities of encryption, and have the magical guidelines reflect that increase in difficulty.

It raises some fundamental questions about encryption and it's intent in the medieval setting; what is the view of encryption? Everyone's thoughts would be welcome. I'm going to keep plugging away at the blog post with my initial set of assumptions.


Not exactly, there's a major difference.

InMe allows you to understand what a given person says because that person knows. You're basically reading his mind, speech center only.

Books have no minds, they are not aware of their own contents - thus Hermetic magic cannot trivially decode written materials.

That said, my (admittedly cursory) research on the subject indicated that in europe, code was limited to the caesar cipher, or word substitutions (often euphemistic). Messages appear more likely to have been hidden than actually encrypted.

However the arabian worl knew of some cryptology and certainly of cryptoanalysis, after the 9th century, courtesy of Al-Kindi.

How far the Hermetic Order has progressed is anyone's guess though.

+1. Which is why there still is a language barrier at all even among magi.

And written in code rather than encrypted.

Disagree, the templars and the church certainly used more complex encrypts. And that´s just what we know about.

I would simply say that magic probably has no easy way of doing this. Magic cant think or even approximate the process. For magic to do it i think it might need a connection with a human brain to be able to make sense of it all, and at that point, the magic part is just something to make it easier/faster.

Back in fourth edition, there were InIm-spells that told you what an artist meant to express with a piece of art. Deciphering a mundane cipher with magic shouldn't be any more difficult than that. A cipher-text is just as mindless as a piece of art. Be aware that decrypting a text does not necessarily mean you understand the decrypted message: "Meet me at the usual place at five o'clock"

Magically encrypting a text has major advantages over mundane encryption: You can transfer the key in a way that can not be intercepted by mundane means. You could have an encrypted text changing its key depending on the sun, the moon, or what the person trying to read it ate this morning. Or enchant a text, so it can only be read by members of your bloodline.

It basically comes down to "who has more Intellego?" and just how many hours you want to waste for your tinkering on codes at the gaming table. Anything more complicated than a monoalphabetic code is pretty much useless for gaming purposes, as it means wasting my precious gaming time that could find better uses otherwise.

Yikes, that´s pretty damn outrageous...

Now that i certainly agree with.

Or you could just use one of the more complex encryptions that you constructed just for the fun of it...
Doesn´t everybody do that? :mrgreen:

That was fourth.
There was a reason they made a 5th edition.

I was hoping for that, could you point me at some examples or sources please?

I don't know if that is necessarily true.

You can talk to rocks, lakes, trees, etc, with suitable Intellego spells so I don't know why you couldn't talk to a book.

The book may or may not be aware of its contents, of course, and it might not be aware of its contents in a way that is helpful to a person (it might know, for example, about the kinds of inks and quills used, and the number of different writers, and the length of time the writing took). Depends on the individual book and its history, I would think.

Note that the practise of magi writing their Lab Texts in an idiosyncratic notation that needs to be translated into plain text before another magus can use the Lab Text is encryption, of a sort.

As a first pass on sources, try these below. Some are very unauthorative, but interesting:

There is also a very large amount of material related to Arabic encryption and due credit for some techniques really is with their culture. Impressive. I am finding a lack of good material though, such as a solid time line of the innovations.

May favorite "encryption" for Ars is from MoH where Conscientia made a message in a bottle.

I think i can say with decent certainty that if you can have magic "translate" any code as suggested, then the same procedure or a similar one will be perfectly capable of using magic to copy books. Anything else would be strange.

A "personal notation system" or "personal shorthand" i think is probably the best definitions?
Using a "real" encryption doesn´t really make sense except for very paranoid and/or secretive magi.

Troublesome, i dont think i have any of the relevant books on it. Though there is some passing mention in my books on military history, that´s not very helpful here. Well i do have a couple on cryptoanalysis, but they dont do history, and another two on crypto and ciphers but the one that goes historical does it generalised.

The online stuff ibt posted covers what i can find online as well so far. I´ll see if i can dig up something more but no promises.

Well Hermetic magic has no problem copying books exactly. It's the side effects of such magic it can't deal with. Specifically the one that seems to kill the saga in 3-4 sessions after such a spell is invented. Then has me and my friends switching to another game system for awhile.

That being said IMS the PC's are currently wrestling with the revelation that the information contained in books (and art) are a form of thought and can be affected by mentem. And that thoughts themselves can be enchanted. Pretty far away from most Troupes view of RAW I admit, but we are trying for weirdness.

I believe I mentioned this?

1553 AD is hardly periode fo 1220

Same for 1466 - and the "height of cryptography at the time"

References the arabs and Al-Kindi (both mentioned above), but does seem to indicate that the europeans mostly start engaging in cryptography in the Renaissance, yes?

If you don't mind being a couple of centuries ahead, sure.

I was rather hoping someone had something on european cryptography in the 900 AD - 1250 AD periode, which I consider more relevant for ArM.


Oh certainly! It would know all these things and plausibly be able to recognize the people who've read it as well.
And whine about never being read/never having time to rest, as appropriate.

Perhaps more accurately, the text has no mind of it's own.

Asking a book what the text inside it means is (to my mind) akin to asking a person to describe each milimeter of his own intestines, in detail and in order.
The bit that hurts is easy enough, so's the "..and they never even bothered to remove that splotch of ink! My finest illustration that was! Just past my middle page! But did they ever even dry it up? Noooo! I tell you, apprentices these days...!"
But the actual text inside? It's specific meaning, translated into something the caster would understand?

Not really.

Just my 2 bits, obviously.

possibly dumb idea...

Fifth edition has come up with Craft Magic, wherein a magus can cast a spell that performs whatever mundane action somebody can come up with without the caster having to know how to mundanely perform the action. Could translation/encryption be shoe-horned into being possible with Craft Magic?

Determining the form is the issue, as always. Rego+Mentem seems appropriate but how does Mentem relate to the Animal/whatever books are made of? Not sure. Perhaps the "work" done by the spell is done on the reader, not the text...


Perhaps not, but consider a book stored for decades in a library in a high magic aura. There is no telling what it might or might not know.

I would have no problems with individual books in a saga knowing their contents, even if most books do not.

I would expect a book on encriptation stored in a high magic aura to be etremely difficult to locate and open after a while. :slight_smile: He might ask for a different password every day, each with an elaborate cypher related to the star configuration INSIDE the aura. or some other weirdo stuff like that. I would call it Dan for extra laughs.


Well if it is silly Rich then I'm as silly as you, as I thought of the same things. :smiley: My approach in the blog post is to provide several ways that the encryption/decryption can be performed, depending on physically what is happening.

For example:

  • If a text is actually being re-written, as if a scribe is editing the page by hand, then Rego (Forms) magic is used, and the Craft Magic rules for difficulty and Finesse apply. Rego Herbam Animal Aquam seems appropriate.
  • If a visual comparison is being made, or the decryption is being temporarily performed then Muto Imagonem is used to re-order the alphabetic symbols in an order prescribed by a cipher key. eg, the image of the text is temporarily changed by Muto magic to switch letters.
  • I'm allowing a degree of complexity for the spells to either use a preset Cipher Key, or use one at cast time. This adds the problem of trading cipher keys between Magi, and potentially how Magi would choose to do that given magical means.
  • I'm allowing for degrees of complexity in the cipher key and the cipher method; but am not happy with my approach yet in terms of translating the complexity of Encryption thinking into Hermetic magnitudes of difficulty.
  • If a "brute force" method is used then the same MuIm switch happens on a block of text, but the spell effect will also compare the resulting random result to words which would be recognisible was proper words by the caster. If translated text is found, then the process pauses and a chime sounds.
  • A new spell cast by the encrypting magus so that their mind is changed so that all written words are re-ordered to be consistent with the cipher key. This removes the need to "edit" a written page afterwards, but means the encryption spell must be known by the writer, or cast on a mundane scribe.
  • I'm still debating the actual types of encryption possible, as some of the more advanced techniques require advanced mathematics, and I am not confident that it suits the game paradigm. Caesar Cipher seems fine (substitution), Sycathe seems fine (tool based re-ordering), and a combination of the two seems fine as well (which actually makes a reasonably complex encryption method). Cipher phrase keys seems OK, but would need to be simple. Character frequency analysis as a concept in decryption is borderline as is was invented around 1000AD but not in Europe. Code-wheel style changing cipher keys seems very doubtful, but I think they are too bloody obvious to not be included. Enigma machine style variable rotor keys, and single use pads are way out.
  • encryption based upon non-alphanumeric aspects, such as designing encrypting spells based upon images, apprentice, bloodline, astrological signs, or arcane connections, etc are all still just considerations.

In short, I've got a fair amount of work to still do, and the blog post is already probably too long for a single post.

cheers IBT.

A fairly easy encriptation method for hermetic magic would be to stain all pages with Moon duraton ink. Nothing can be read until the spell wears of or you dospell it. Good anti mundane mehod though it is very bad for hermetics.