Are you trying to upload your .aab file to the Google Play Store for publication? You might see the error that says :
"Android App Bundle uses an upload certificate with a key that is too weak."
Good news. I discovered an amazing Android app that lets you create a new Keystore, and you can sign your own .aab file for uploading to the Play Store. 
The developer of the app provides a YouTube Playlist to tell you how to use it properly. 👍
It might cost you about $2. But, it is well worth it.