Outline for April 14, 1997

1.	Greetings and Felicitations

2.	Simple substitution ciphers

a.	Do Caesar cipher

b.	Go through how to break it

c.	Present VigenĖre tableau

d.	Discuss breaking it (Kasiski method). Note index of coincidence is probability 2 
letters chosen at random from ciphertext are alike

e.	Generalize to very long keys and show running key and autokey

f.	Go through rotor systems (Enigma)

g.	Go through one-time pads

3.	Polygram substitution cipher: Playfair

a.	Key is 5 by 5 grid

b.	If m1, m2 in same row, c1, c2 are to immediate right of m1, m2 respectively

c.	If m1, m2 in same column, c1, c2 are below m1, m2

d.	If m1 = m2, insert null in text

e.	if m1, m2 in different rows and columns, c1, c2 form rectangle with c1 in m1¼s row 
and c2 in m2¼s row

f.	if odd number of characters in message, append null.