You must be the original encrypter of the file or a designated recovery agent for the file to use the following steps. If you are not authorized to remove encryption, you receive the following error message:
Error Applying Attributes
An error occurred applying attributes to the file:
Access is denied
To remove encryption from a file: 1.Use Windows Explorer to browse to the location of the encrypted file that you want to decrypt. 2.Right-click the encrypted file, and then click Properties. 3.On the General tab, click Advanced. 4.Click to clear the Encrypt contents to secure data check box, click OK, and then click OK again.
I believe that the key file is for removing the encryption if you are not the original person (account) that encrypted the file in the first place. It can also be used to give a third party access to the contents of the file.