keydb.cfg contains disc keys to decrypt Blu-rays, please Google keydb.cfg for more details. The latest Blu-ray may require new keys to be decrypted, you will need to keep it updated.
The default keydb.cfg location is %APPDATA%\aacs\, you can change it in Xreveal's Settings > BD / UHD > KeyDB.
The Pro version doesn't need keydb.cfg. Some discs may require an internet connection to retrieve keys.
Please download and install Xreveal Plugins 1.0 if you want to remove BD+ protection offline.