WARNING! There are some things in these slides that I need to clean up as they made sense in the context of a lecture but, upon review, don't work as stand alone material. I'll get those updated when I can. Send me an email if you have any questions.

The actual breakdown for the class is about 5 minutes of intros, 40 minutes of lecture, and another 5 showing how to break a basic substitution cipher and chatting.


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I do have some sources that I will reference from beyond 1600 that are reprints or slight modifications of previous works. Porta comes to mind here.

This is taken from Singh, p30.

We’re going to be focusing on the elements in dark blue. Stenographic approaches are outside of the context of this discussion.




Every engineer: mechanical, electrical, hydro, etc. is an ‘engineer’ first. And all engineering is born of CIVIL engineering. This is just my opinion, but I stand by it.


This is where the seemingly ridiculous 5000BCE number above comes from. Unfortunately I cannot remember the original source for this. I was going through some of my notes and re-discovered a margin comment that simply said 'Ancient China, 5000ish, poop notes!'. I know it's not 'researched', but if I come across that source you can bet your tupence that I'll back this out, it's a funny anecdote that I just had to throw in.

There are dozens of different Viking/Norse/What-have-you systems that have been identified. This is not my area of expertise. I know a bit about Jötunvillur (see the ciphers section) but that's about it. When I started to scratch the surface here I encountered too many conflicting theories and opinions to get a real understanding of the topic. I'm happy to share what I know but this is a class on its own, easily.


Great read: https://www.the-parallax.com/2016/01/05/encryption-over-time/

Great reads:
http://www.cryptool-online.org/index.php?option=com_content&view=article&id=148&Itemid=386&lang=en
https://en.wikipedia.org/wiki/Mlecchita_vikalpa
http://bharatkalyan97.blogspot.com/2014/02/64-arts-of-kamasutra-including.html






I make it clear in the class that what I'm referring to here is the idea of a reusable device that can be used to encode messages mechanically. The 'first' cipher wheels show up in the 1460s (Alberti)


Select the horizontal row of the letter then vertical column.

It is important to point out here that I'm talking about western cryptology. There was a considerable advancement in cryptanalysis around 850~ when Al-Kindi published Risāla fī Istikhrāj al-Kutub al-Mu'amāh (رسالة في استخراج الكتب المعماة; literally: On Extracting Obscured Correspondence, more contemporary: On Decrypting Encrypted Correspondence ) This was a great leap forward in concepts such as frequency analysis, but I am not currently knowledgeable in this particular area.





What I intended to say here was 'poly-alphabetic ciphers CAN be created using this tool' Alberti's version consisted of two simple copper discs with the alphabet inscribed along the edges. A needle held the two together and allowed the user to, basically, create Rotational (ROT or Ceaser) ciphers with ease. Again, the CONCEPT here but the implementation came a bit later. To make this even MORE confusing; Alberti used this single cipher tool to create poly-alphabetic ciphers on the fly. He describes using numbers or capital letters within the cipher text to denote which other encoding set to use next. This makes my head hurt too. The final system 'is' poly-alphbetic but the technique is mono-alphabetic. Does that make sense?

When we say 'discussed' you should read that as 'exhaustively documented'. Someday I will go through and count all of the various substitution ciphers that he presents. My guess is that it is well over a dozen

This example from WikiPedia was chosen to point out the similarities between the work of Trithemous and what would come to be known as the Vigenere cipher.

The decoded message is discussed in class as a 'permutation' of the underlying source. For the purpose of general discussion you can think of grills as a kind of transposition cipher.

For example:

 S E C R E T A B D F G H I J K L M N O P Q T U V W X Y Z
 Z S E C R E T A B D F G H I J K L M N O P Q T U V W X Y
 Y Z S E C R E T A B D F G H I J K L M N O P Q T U V W X
 X Y Z S E C R E T A B D F G H I J K L M N O P Q T U V W
 W X Y Z S E C R E T A B D F G H I J K L M N O P Q T U V
 V W X Y Z Z S E C R E T A B D F G H I J K L M N O P Q U
 ... AND SO ON
 

This provides a simple mechinism for introducing quasi-randomness to the 'key space' (for want of a better term).





Another important addition was the implementation of an 'auto-key'. This is discussed at length in class. That 'uses keyword' part is major. Vigenere may have ripped off Belaso but he did make notable contributions to the science, even if those aren't the ones his name is attached to.

Did you solve it? Good for you!
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