Alice and Bob want to communicate securely over an insecure channel where Evecould be listening. To ensure their message remains confidential, they decide to usea simple substitution cipher for encryption and decryption, where each letter in thealphabet is shifted by a fixed number of places.For this exercise, use a shift of 3 places to the right (a Caesar Cipher). For example,'A' becomes 'D', 'B' becomes 'E', 'Z' becomes 'C', and so on. Spaces and punctuationare not encoded; they remain unchanged.Alice wants to send the following message to Bob: "HELLO WORLD".a. Encrypt Alice's message using the specified shift. Provide the encrypted text.………………………………………………………………………………………………[1]b. Discuss the security of using the Caesar Cipher for encrypting messages.Consider scenarios where Eve knows or does not know the method ofencryption.……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………[1]
Question
Alice and Bob want to communicate securely over an insecure channel where Evecould be listening. To ensure their message remains confidential, they decide to usea simple substitution cipher for encryption and decryption, where each letter in thealphabet is shifted by a fixed number of places.For this exercise, use a shift of 3 places to the right (a Caesar Cipher). For example,'A' becomes 'D', 'B' becomes 'E', 'Z' becomes 'C', and so on. Spaces and punctuationare not encoded; they remain unchanged.Alice wants to send the following message to Bob: "HELLO WORLD".a. Encrypt Alice's message using the specified shift. Provide the encrypted text.………………………………………………………………………………………………[1]b. Discuss the security of using the Caesar Cipher for encrypting messages.Consider scenarios where Eve knows or does not know the method ofencryption.……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………[1]
Solution
a. Alice's encrypted message using a Caesar Cipher with a shift of 3 places to the right would be: "KHOOR ZRUOG".
b. The security of using the Caesar Cipher for encrypting messages is relatively low. This is because it is a monoalphabetic substitution cipher, meaning that each letter in the plaintext is replaced by a letter with a fixed number of positions down the alphabet. This makes it susceptible to frequency analysis, where an attacker could potentially decipher the message by analyzing the frequency of each letter in the ciphertext.
If Eve knows the method of encryption, it would be very easy for her to decrypt the message. She would simply need to shift the letters in the opposite direction to retrieve the original message.
If Eve does not know the method of encryption, it might take her a bit longer to decipher the message. However, given that there are only 25 possible shifts (in the English alphabet), she could easily try all possibilities until she finds a message that makes sense.
Therefore, while the Caesar Cipher might be useful for encoding messages in a way that prevents casual eavesdropping, it should not be relied upon for secure communication.
Similar Questions
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