Prove that if only a single character is encrypted

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Reference no: EM131241492

In this exercise, we look at different conditions under which the shift, mono-alphabetic substitution, and Vigenre ciphers are perfectly secret:

(a) Prove that if only a single character is encrypted, then the shift cipher is perfectly secret.

(b) What is the largest message space M for which the mono-alphabetic substitution cipher provides perfect secrecy?

(c) Prove that the Vigenre cipher using (fixed) period t is perfectly secret when used to encrypt messages of length t.
Reconcile this with the attacks shown in the previous chapter.

Reference no: EM131241492

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