CNG Service Defaults in Windows 8
Kernel Cryptography, Next Generation by Microsoft Corporation.
The CNG service is a kernel device driver. In Windows 8 it is being loaded by Boot Loader before Kernel initialization. If CNG fails to load or initialize, the error details should be automatically logged. Then Windows 8 is restarting the PC and attempting to use the Last Known Good configuration. If the Last Known Good configuration isn't working properly, Windows 8 startup ends with a Stop error. If you disable the CNG service, Windows 8 will fail to start.
Restore Default Startup Configuration for CNG
1. Select your Windows 8 edition and update pack, and then click Download.
2. Save the Win8_CNG_Service_Startup.cmd file to a local storage device.
3. Run the saved file as an administrator.
4. Restart the computer.
The CNG service is using the cng.sys file that is located in the %WinDir%\System32\Drivers folder. If the file is corrupted or deleted, you can put it back in there.