Trying to solve to problem, but have no idea where to start from.
One of the simplest methods to encrypt a message is by using a key that defines how many positions the letters in the text is replaced. If you encrypt a text with a key 3, all letters in the original text moves down the alphabet by 3 positions. If you decrypt a text with a key 3, all letters in the decrypted text moves up the alphabet by 3 positions (i.e d a ; f c; etc )
e.g if you encrypt the text ?trial? with a key of 3, it will become ?wuldo? if you decrypt the text ?wuldo? with a key of 3, it becomes ?trial?
(a) Write an M-file to can decrypt the following message ?brx pdqdjhg wr gr lw.? using a key of 3. (b) Write an M-file that can load the text file ?encrypted_text.txt?
Notes: i. Only alpha-characters have been encrypted. Punctuations and white spaces have not been altered and as such in your codes, you should not decrypt any punctuations or white spaces. ii. The alphabet has 26 letters. So your encryption key should always be between 1 and 26. iii. You might use MATLAB inbuilt function ?find? iv. See more hints in the lab4presentation file on moodle