An EBK extension is used by the software eBook Pro Viewer when it saves an e-book file. The eBook Pro is a software which can create eBooks and protect copyrighted information. An EBK file contains the encrypted and compressed version of an e-book which can be read using eBook Pro Viewer; after providing appropriate credentials for authentication.
Information about EBK file generating software
The eBook Pro Viewer is an app that can view typical formats of e-books. By using it the customers will be able to distribute their publication in more professional and secure way. This software will take the input as HTML, compress it, and encrypt it so that the files cannot be copied or pasted, or accessed by unauthorized users. The customers can also control eBook distribution using the eBook Pro Client Tools software, which allows to manage user access permissions online. Therefore the support of Ebook Pro Viewer seems to be no longer available.