My question is so similar to this question:
I tried the solution like the selected answer(by omar ram), but I chose accidentally "1. Continue boot" at "Perform MOK Management" setting(blue window). After that, the setting window "Perform MOK Management" don't appear so I can't enroll key. Moreover I can't boot ubuntu now(after “Booting in insecure mode” is display, black screen continues forever with blink cursor).
How can I enroll key in this case? If "Perform MOK management" setting window is shown again, I can input the password for the key and this issue will be solved.
Ubuntu 16.04 LTS
NVIDIA GeForce GTX1080