rebel_cipher.md

The Rebel Cipher Algorithm

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Welcome to my Rebel Cipher Algorithm which takes in an input of a string, encrypts it based on your given encryption key, and writes it to a file known as encrypted_message.txt

The Encryption Function

Here we convert the message into barebones raw value which we leave consistent throughout our code. This includes checking if the message is Uppercase, if it is Lowercase we use the .upper() method in order to convert the values into a UPPERCASE Value.

We the convert the encrypted characters (the values) into their respective ASCII values, by using the chr((ord(char) - 65 + key)%26 + 65) function in order to convert it into the numerical ASCII value which we will convert later.

Then the function returns the value of the encrypted message

def encrypt(message, key):
   encrypted_message = ""
   for char in message:
     if char.isalpha():
      is_upper = char.isupper()
      char = char.upper()
      encrypted_char = chr((ord(char) - 65 + key) % 26 + 65)
      if not is_upper:
        encrypted_char = encrypted_char.lower()
      encrypted_message+=encrypted_char
     else:
      encrypted_message+=char
   return encrypted_message

The Decryption Function

The Decryption Function is fairly similar, it returns the encrypted value; except we have a -key value which basically flips the value of the key so that it is decrypted from the original key (if it added 5, the decryption subtracts 5)

def decrypt(encrypted_message, key):
  return encrypt(encrypted_message, -key)

The Saving Function

That was a funny name for a function... In this we have the function which saves the data to a file which we haven't specified. An important note: we are using the "w" function so that we are able to write to the given file.

def save_to_file(data, filename):
  with open(filename, "w") as file:
  file.write(data)

The Reading Function

We do a similar thing as above, except now we are only "r" or reading from the file. Since this is a simple code example, it is not really necessary for us to do this; but as a good programming practice, it is important to only use the file in the way you want it to be specified.

def read_from_file(filename):
  with open(filename, "r") as file:
  return file.read()

Main Loop

In this, we take the user input and ensure that it is not a number through the following

while not valid_message:
  message = input("Enter the Message> ")
  if any(char.isdigit() for char in message):
    print("This was an invalid input, please try entering a LETTER VALUE")
  else:
    valid_message = True

In here all we are doing is ensuring that we have a value that ISN'T a number through the .isdigit() method. If it is a number, we ask them to give another input; if it isn't a number, then we allow the programming to continue running by breaking out of the while loop by setting the Boolean Expression of the while loop to TRUE

Next, we are gathering all our various inputs

key = int(input("Enter the Encryption Key> "))
  
encrypted_message = encrypt(message, key)
decrypted_message = decrypt(encrypted_message, key)

And finally, we are printing out all our values; just converting them to Uppercase by using the .upper() function once again:

print(f"Your encrypted message is: {encrypted_message.upper()}")
print(f"Your decrypted message is: {decrypted_message.upper()}")

save_to_file(encrypted_message, "encrypted_message.txt")

encrypted_message_read_from_file = read_from_file("encrypted_message.txt")
print(f"The message read from the file is {encrypted_message_read_from_file.upper()}")