Answer to Question #63412 in Discrete Mathematics for chenwei

Question

Suppose that you need to deliver the message “161803398” which is the pass key for a weapon
activation to country X. Encrypt the message using Caesar cipher with the encryption key,
(n + 2^2 )mod10 where n =0, 1, 2,...,9 , without being intercepted and decrypted by other countries. Using number theory method:
(a) State the decrypted message.
(b) Determine the decryption key.
(c) Suggest an improvement to the encryption key to increase the encryption strength