[Q] Enable USB Debugging tools through ADB in recovery mode topic

So, my digitizer is broke and I can't see anything or use the touch.

I am able to get into recovery mode with ADB and I tried some echo lines to manually activate debug mode, so that I can have my device authorized to use with ADB afterwards.
I'm trying to use Androidscreencast, but I need to make it work with ADB first and since I get device unauthorized it means that I don't have usb debugging enabled.

The final question : How can I activate debug mode without a screen?