lect2 Lecture 2
"Definitions of Classical Ciphers"

Here are the lecture notes for this lecture (written by Il'ya  Safro  with my editorial help).
You may also visit the site of the ACA (see Chapter 8). It contains the ciphers that were
shown in the class and much more.  A good historic survey is in Encyclopaedia Britannica.
So far we have seen Kerchoff's Rules of Cipher Design and  a classification of the substitution
ciphers. Some classic ciphers that we've seen:

Transposition (permutation)  ciphers:
   Nihilist transposition, Railfence (civil war cipher), Redefence

Simple substitutions:
   Baconian,  Polibius, Checkerboard

Digraphic simple substitutions:
   Porta's digraphic table (1563),  Playfair (Wheatstone's digraphic square, 1854) ,

Poly-alphabetic substitutions:
  Vigenere (Lewis Carroll's variant) , Vigenere (admiral Beaufort's variant, 1857),
  Autokey (the original Vigenere's cipher, 1523)

Homophonic substitutions:
  Grandpre, Homophonic

Multileteral-substitution
  Key phrase

Chapter 1  (sections 1.4 and 1.5) of the Handbook of Applied Cryptography, is still relevant.

In the next lecture we will turn to the analysis of some of these ciphers.