"Ar " <firstname.lastname@example.org> wrote in message <email@example.com>... > 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
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