You possess to compel a program that encrypts and decrypts intimations. Probably the easiest way of doing this would be to use a Ceaser nonentity.
When the program starts it deficiencys to ask the user if they lack to encrypt a intimation, decrypt a intimation or to exhibition the stored intimation. For these ability to effort the user obtain deficiency to apprehend the key to solving the nonentity and obtain deficiency to invade that forthcoming selecting an non-interference.
(Example: If using a Ceaser nonentity the user deficiencys to apprehend how multifarious spaces to shelve the alphabet so it lines up appropriately.)
So this moderation that you possess to present the key to me when you despatch the edict.
The stored intimation is, "Enryption or decryption auspicious. This plan is alert for raise testing of intimations."
If the user selects the non-interference to exhibition the stored intimation, forthcoming accepting the key from the user, the program should show this intimation in its encrypted conceive and in its decrypted conceive.
Also I possess to see the basic construction of the forthcoming items.