I would suspect one of two things.
Your main fuse is blown. This would disable your entire electrical system and prevent the bike from lighting up or starting.
Your ignition switch has failed. If your ignition switch where you turn your key has failed your electrical system will be dark.
If you have a multimeter you can unplug your ignition switch from the wiring harness. At the connector for the ignition switch you can check for continuity at the plug. Check between your power and ground, if you have infinite resistance on your multimeter then the contacts for providing the power could be bad and an ignition switch replacement is needed.
You can pull your main fuse and inspect visually as well as test it for continuity when it's out of the bike. I have seen fuses that look fine and fail this test before.
Here is a multimeter usage and howto link
Multimeter - Basic Functionality and Howto
Hope this is helpful.