10 Questions
What is the probability distribution of message space for the shift cipher instance described?
Pr[M=a]=0.25, Pr[M=b]=0.5, Pr[M=c]=0.25
What is the correct statement regarding the probability of the ciphertext 'D' and 'E' in the given shift cipher instance?
Probability that the ciphertext is “D” is the same as the probability that the ciphertext is “E”
What is the incorrect statement about the probabilities in the given shift cipher instance?
The probability that the ciphertext is 'D' is 126
In the given shift cipher with the provided probability distribution, what is the likelihood of generating a message 'A'?
Lower than that of 'B'
Which statement correctly compares the probabilities of 'D' and 'E' in the shift cipher instance?
'D' has half the probability of 'E'
Which of the following encryption schemes is not perfectly secure?
Vigenère Cipher
In a perfectly-secure encryption scheme, which condition is valid?
Pr[M=m|C=c] = Pr[M=m]
In a Vigenère cryptosystem, if the word 'CRYPTOGRAPHY' occurs twice in a 500-character encrypted message, what is the length of the encryption key?
6
Which statement is correct about encryption schemes?
(I) Any encryption scheme with key length less than message length cannot be perfectly secure.
Which of the following conditions is necessary for perfect security in encryption?
Changing keys after every few messages
Test your knowledge on the security of encryption schemes by answering questions about perfectly secure and not perfectly secure encryption schemes, as well as valid conditions for a perfectly-secure encryption scheme.
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