Question

(a) Classical Ciphers: Consider the message "I FOUND THE SECRET". Encrypt the message using the following ciphers. Assume plaintext, ciphertext, and keys are all capital English letters: A = 0, B = 1………………. Z = 25. Keep spaces as is.:

A Shift (Caesar) cipher with key H.

(b) Given the problem from question (a), write a program, in any language you like, to decrypt messages encrypted such cipher. Both the message and the key should are inputs to the program.

Answer 1

To encrypt the message using the Caesar cipher with key H, shift each letter 7 positions to the right. To decrypt, shift each letter 7 positions to the left. A program can be implemented to decrypt Caesar cipher messages.

Step-by-step explanation:

To encrypt the message using the Caesar cipher with key H, we will shift each letter in the message by 7 positions to the right in the alphabet. So, 'I' becomes 'P', 'F' becomes 'M', and so on. The encrypted message will be 'P MSZBU WMPA ZOHZLU'.

To decrypt the message encrypted with the Caesar cipher, you would need to shift each letter in the ciphertext by the same number of positions to the left in the alphabet. In this case, you would need to shift each letter by 7 positions to the left to get the original message, 'I FOUND THE SECRET'.

A program to decrypt messages encrypted with the Caesar cipher can be implemented in any programming language. The program would take the ciphertext and the key as inputs. It would then shift each letter in the ciphertext by the negative value of the key to decrypt the message.