Try This: More Combinations

Just as a PIN is stronger with an increased number of combinations, so is the cipher. The ascii_shift cipher has more combinations.

Duplicate radio_send_images_caesar_key_unknown as radio_send_images_caesar_key_unknown_try_this.
Duplicate radio_receive_images_caesar_brute_force as radio_receive_images_caesar_brute_force_try_this.
Replace the caesar functions in both programs with the ascii_shift function from the Cybersecurity: Encryption Intro tutorial’s ASCII Shift Cipher activity.
Replace the call caesar(key, packet) blocks from both programs with call ascii_shift(key, packet) blocks.
In radio_send_images_caesar_key_unknown_try_this, change set key to (pick random (1 to 25)) to set key to (pick random (1 to 93)).

To crack the cipher, your project will have to examine more combinations.

In radio_receive_images_caesar_brute_force_try_this, change for key in (range start(-1) end (-26) step (-1)) to for key in (range start(-1) end (-94) step (-1)).

You might notice an upper-case HAPPY as well as a lower-case happy. The key that generates the upper-case HAPPY is the correct answer, though either might actually work for a sniffing attacker’s purposes. This is an additional weakness of the ASCII Shift cipher. Make sure not to choose a key that will simply encrypt your upper-case characters as lower-case or vice-versa.