When you install the extension, you'll have a few keys set up by default. Visit http://www.reddit.com/r/shadowcryptplayground/ to see if everything is working right. Join our mailing list to discuss the extension.
Press Ctrl+Space to turn encryption on and off in a text field. You'll want to turn it off for things like usernames, email addresses, and CAPTCHAs.
Extra Secure Input
With a text field focused, press Ctrl+` (next to the "1" on your keyboard) to open a dedicated input window. Use this if the page is trying to interpret your text as keyboard shortcuts.