The rdk files are related to RIM client registration files for Blackberry devices.
RDK file extension - Blackberry RDK data
What is rdk file? How to open rdk files?
File type specification:
The rdk file is related to a special client registration files that look like this client-RDK-xxxxxx.csj.
So RDK is not an actual file extension, however the "RDK fie" query appears frequently in our search logs.
This rdk file type entry was marked as obsolete and no longer supported file format.
This type of file is no longer actively used and is most likely obsolete. This is typically the case for system files in old operating systems, file types from long discontinued software, or previous versions of certain file types (like documents, projects etc.) that were replaced in higher versions of their original programs.