Hello, i have a lot of experience with encryption, decryption and making GUIs, i am pretty sure i will be able to help you, just send me a message.
I will use real encryption, not easy to break algorithms like base64 (which is not even a real encryption method, it is an encoding method) or md5 (which is a oneway encryption method, that means that you can not get the information back) I will use stronger encryption, I can use RSA, Fernet, Hardcore Vigenere and much more.