"Shannon's theory of Secrecy Systems. Plaintext Recognition."

Claude Shannon

After the lecture notes are written in light green.

1. We will finish the analysis of the Enigma cipher (in the first 10-20 minutes
we'll discuss Gillogly's ciphertext-only attack on Enigma [handout]).

2. In cases of automatic cryptanalysis of ciphers, plaintext recognition plays an
important role (as you may have already seen, while doing the homework).
You can look here for some of the material that we will discuss. Statistical
analysis of simple ciphers is covered well in Alan Konheim's book
"Cryptography, A Primer".

3. We will discuss Shannon's "Theory of Secrecy Systems" [online] (1945-48),
and  intuitive  principles for cipher design he put forward (confusion & diffusion).
This is also closely related to his "Mathematical Theory of Communications".
[online!] where the notion of entropy is studied in the context of information
theory. [We have discussed redundancy of the English language, and the notion
of  Unicity distance of a cipher.]

4. [handout  with DES]
 

Reading

1. Claude Shannon,  "Mathematical Theory of Communications [online!]".
2. Claude Shannon, "Theory of Secrecy Systems" [online]
3. Alan Sherman, "Statistical techniques for language recognition: An introduction and guide for cryptanalysis".
4. Alan Sherman, "Statistical techniques for language recognition: An empirical study using real and simulated English".

The next lecture continues this topic.