Show the computations employed with the index of coincidence method to retrieve the second password character of a Vigenere encryption for a language where:

Alphabet: {A,B}, fA=80%, fB=20%,

Assume password is length 3 [_,_,_]

Ciphertext: A|A|A | B|A|A | A|B|A | B|A|B | A|A|B

a) What is the index of coincidence of this language?

b) What is the index of coincidence of the ciphertext (password length 1)?

c) What is the IOC value for A being the second password character

d) What is the IOC score for B being the second password character

e) What is the hypothesized second password character