Create a personal ID code
The first time that you launch MarpX Privacy, you should see this page:
Notice the instructions in the upper part of the screen...Create a seven character personal ID code. Use any of digits 0-9 or letters A-Z a-z. Case matters: 'B' is not the same as 'b'. Example: 5rT9xLD is different from 5RT9XlD. You will need to input this code every time that you want to use the automatic key option when you enter the program. For your ongoing security, do not give your personal ID code to anyone.
Why your ID code is important
"Why should I be so careful with my personal ID code?" For this reason: It protects details in your list of confidants. If a malevolent person learns the authentication code for sharing of files and messages between you and someone else, that can be bad. If you don't have the Extreme Encryption add-on for the relationship between you and that confidant, then a hacker can get at any content that the two of you have already exchanged and may exchange in the future.
Please don't leave your personal ID code on a sticky note on your computer, or anywhere in or on your desk where other people may get at it. The personal ID code is short; memorize it. In worst case, keep it in a good quality password manager, and don't let the the password manager's master code become known to anyone.
Only code you need to remember
You will see authentication codes, one for each confidant relationship that you will build in the future. In that sense, you may see a lot of codes. But those authentication codes can each be forgotten the moment you and a confidant have tested exchanging a test message.
There is more. As long as you use the Automated Keys feature, you will never even see a key. There are no keys, and the authentication codes you can quickly forget. So there is only the one code that has to remain in your memory, your personal ID. That simplifies life a bit.
If you must change your code
What if someone somehow gets hold of your personal ID code and compromises your security? It helps if you make a habit of occasionally backing up your roster file, each time using some new seven character combination of A to Z, a to z, and 0 to 9. If you have not done so, back it up quickly the moment you know that your ID code has been compromised. Note very carefully the key that you use for this backup. Next, delete or change the name of the file "roster.txt.enc". Then move your latest backup of the roster into place and change its name to "roster.txt.enc".
That's a little tricky if you are not accustomed to changing file names. (The nearest computer-savvy teenager may be able to help you.) The next step clarifies what is going on. Launch MarpX Privacy again. This time, instead of your usual personal ID code, enter the key that you used for that latest backup of the roster. That key has become your new personal ID code. The person who broke into your system is now locked out again. Use this new personal ID code into the indefinite future.