Consider the following two streams of text y and z. y = the man in black fled ac

Question

Consider the following two streams of text y and z.
y = the man in black fled across the desert and the gunslinger followed z = hello my name is inigo montoya you killed my father prepare to die
Fine the index of coincidence I(y,z). For stream z, evaluate I(z,z^(+4)) and I(z,z^(+7)) Consider the following two streams of text y and z.
y = the man in black fled across the desert and the gunslinger followed z = hello my name is inigo montoya you killed my father prepare to die
Fine the index of coincidence I(y,z). For stream z, evaluate I(z,z^(+4)) and I(z,z^(+7))
y = the man in black fled across the desert and the gunslinger followed z = hello my name is inigo montoya you killed my father prepare to die
Fine the index of coincidence I(y,z). For stream z, evaluate I(z,z^(+4)) and I(z,z^(+7))

Explanation / Answer

Index of Coincidence is a cryptanalysis technique studying the probability of finding repeating letters in a ciphered text. A text in English language has a coincidence index of 0.0667
Lets y = the man in black fled across the desert and the gunslinger followed

Letters count

E   8
L   5
N   5
T   4
D   4
S   4
A   4
R   3
H   3
O   3
G   2
C   2
F   2
I   2
W   1
U   1
M   1
K   1
B   1

Using Index of coincidence formula: the output y = 0.055194

z = hello my name is inigo montoya you killed my father prepare to die

Using Index of coincidence formula: the output Z =0.057302

index of coincidence I(y,z)=I(0.0551,0.0573)

evaluation1
I(z,z^(+4)) = I(0.0552,0.0552^(+4))
= I(0.0552,0.000011)

evaluation2
I(z,z^(+7))=I(0.0552,0.0552^(+7))
       =I(0.0552,0)

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