This application allows users to save and encrypt their secret notes using a master key. It provides functionalities to both save notes by encrypting them and decrypt previously encrypted notes using the same master key.

secret_notes_app.py

from tkinter import PhotoImage, messagebox, Canvas, Button, Entry, Label, Text, END, Tk
import base64

def encode(key, clear):
    """
    Encrypts the given text using Vigenere cipher with the provided key.

    Args:
        key (str): The encryption key.
        clear (str): The text to be encrypted.

    Returns:
        str: The encrypted text.
    """
    enc = []
    for i in range(len(clear)):
        key_c = key[i % len(key)]
        enc_c = chr((ord(clear[i]) + ord(key_c)) % 256)
        enc.append(enc_c)
    return base64.urlsafe_b64encode("".join(enc).encode()).decode()

def decode(key, enc):
    """
    Decrypts the given text using Vigenere cipher with the provided key.

    Args:
        key (str): The decryption key.
        enc (str): The text to be decrypted.

    Returns:
        str: The decrypted text.
    """
    dec = []
    enc = base64.urlsafe_b64decode(enc).decode()
    for i in range(len(enc)):
        key_c = key[i % len(key)]
        dec_c = chr((256 + ord(enc[i]) - ord(key_c)) % 256)
        dec.append(dec_c)
    return "".join(dec)

def save_and_encrypt_notes():
    """
    Saves and encrypts the entered notes using the provided master key.
    """
    title = title_entry.get()
    message = input_text.get("1.0", END)
    master_secret = master_secret_input.get()

    if len(title) and len(message) and len(master_secret):
        message_encrypted = encode(master_secret, message)

        try:
            with open("mysecret.txt", "a") as data_file:
                data_file.write(f'\n{title}\n{message_encrypted}')
        except FileNotFoundError:
            with open("mysecret.txt", "w") as data_file:
                data_file.write(f'\n{title}\n{message_encrypted}')
        finally:
            title_entry.delete(0, END)
            master_secret_input.delete(0, END)
            input_text.delete("1.0", END)
    else:
        messagebox.showinfo(title="Error!", message="Please enter all information.")

def decrypt_notes():
    """
    Decrypts the entered encrypted notes using the provided master key.
    """
    message_encrypted = input_text.get("1.0", END)
    master_secret = master_secret_input.get()

    if len(message_encrypted) == 0 or len(master_secret) == 0:
        messagebox.showinfo(title="Error!", message="Please enter all information.")
    else:
        try:
            decrypted_message = decode(master_secret, message_encrypted)
            input_text.delete("1.0", END)
            input_text.insert("1.0", decrypted_message)
        except:
            messagebox.showinfo(title="Error!", message="Please make sure of encrypted info.")

# UI setup
window = Tk()
window.title("Secret Notes")
window.config(padx=30, pady=30)

canvas = Canvas(height=200, width=200)
logo = PhotoImage(file="topsecret.png")
canvas.create_image(100, 100, image=logo)

title_info_label = Label(text="Enter your title", font=("Verdena", 20, "normal"))
title_entry = Entry(width=30)
input_info_label = Label(text="Enter your secret", font=("Verdena", 20, "normal"))
input_text = Text(width=50, height=25)
master_secret_label = Label(text="Enter master key", font=("Verdena", 20, "normal"))
master_secret_input = Entry(width=30)
save_button = Button(text="Save & Encrypt", command=save_and_encrypt_notes)
decrypt_button = Button(text="Decrypt", command=decrypt_notes)

canvas.pack()
title_info_label.pack()
title_entry.pack()
input_info_label.pack()
input_text.pack()
master_secret_label.pack()
master_secret_input.pack()
save_button.pack()
decrypt_button.pack()

window.mainloop()