1. The Simple Substitution Cipher is a major improvement on the Caesar Cipher. a
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Question
1. The Simple Substitution Cipher is a major improvement on the Caesar Cipher.
a. In what different ways is it an improvement?
b. If a Simple Substitution Cipher is used (with an unknown key) and we intercept the ciphertext OXAO then which of the following four-letter words could be the plaintext: JOHN, SKID, SPAS, LOOT, PLOP, OSLO?
c. If a Simple Substitution Cipher is used (with an unknown key) and we intercept the ciphertext BRKKLK then what do we know about the plaintext?
d. Suppose that in the case of intercepting BRKKLK we also know that the plaintext is the name of a country. What is the plaintext?
e. What important lesson does the BRKKLK example illustrate?
Explanation / Answer
A) In caeser cipher we substitute a letter with another but in sequential manner as: --------
A to Z will be substituted as F to Z And A to Z respecively. but in simple substitution cipher we choose any letter from the alphabet which is not used earlier as RAM will be Substituted as DRW.
B) the plain text will be SPAS because two same letter will take same substitute through out the message.
C) we know that in plain text their is 3 same letter occured in position 3,4 and 6 .
D) Greece will be the plain text.
E) That if we know the frequency of letter and if we have same letter occur multiple times we can easily crack the cipher.
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