CNG Service Defaults in Windows 10
Kernel Cryptography, Next Generation by Microsoft Corporation.
CNG is a kernel device driver. In Windows 10 it is starting by the operating system Boot Loader as a part of the driver stack for the boot volume. If CNG fails to load or initialize, Windows 10 attempts to record the error details into Event Log and restart the PC, using the Last Known Good configuration. If the Last Known Good configuration cannot be applied or working improperly, Windows 10 startup process halts with a Stop error. If you disable or delete the CNG service, Windows 10 won't start.
Restore Default Startup Configuration for CNG
1. Select your Windows 10 edition and release, and then click Download.
2. Save the Win10_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 changed, damaged or deleted, you can restore its original version from Windows 10 installation media.