Answer: Secret Code #171

The secret message says:

FUN

The shift was 5.

The secret note decoded: FUN
The note, decoded.

Letter by letter

Secret letterKSZ
Real letterFNU

Decode it with Python

This program does the decoding for you. Change the secret and the shift to crack other messages!

secret = "KZS"
shift = 5
message = ""

for letter in secret:
    if letter.isalpha():
        number = (ord(letter) - ord("A") - shift) % 26
        message = message + chr(number + ord("A"))
    else:
        message = message + letter

print(message)

When you run it, it prints:

FUN

Did you know? Shift codes are very old. A Roman writer called Suetonius said that Julius Caesar wrote secret letters by shifting the alphabet by three. That’s why it’s often called the Caesar cipher.