Breaking The Substitution Cipher

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Breaking The Substitution Cipher
One way to break a substitution cipher is to use frequency analysis. Let’s focus on the English language for now but the process works the same way for other languages.  The character “e” occurs 12.7% in the Eglish language and the letter “t” occurs 9.35% and the letter “a” is 8.2% of the time.  So, you can count each character in the ciphered text, compute its frequency and start replacing it.  After you complete the first say 4 characters, you may want to change your strategy.  Can you explain why you want to stop after the first 4 characters? The two-character “of” is about 4.16% and “to” is about 2%.  Now try three characters frequency.
After a period of time, you will be able to decipher most of the text.  I am going to ask you to do your first significant homework using frequency analysis.

One possibility for the substitution cipher:
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z


























V
J
Z
B
G
N
F
E
P
L
I
T
M
X
D
W
K
Q
U
C
R
Y
A
H
S
O

Note that we can have 25 factorial of these possibilities (remember 2^88 – 28-bit key)

Here is your homework – A character sub was used. Can you decipher as much of this text as you can? Submit your results in the drop box. You may use Python to code the solution.
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