I've only worked with canvas but not the security stuff, so I can only answer you partially.
Canvas is an element that you can create with HTML5, and the HTML5 canvas data just means what has been drawn on the canvas.
Now for the FPP, RFP stuff, I'm guessing they are some ways to encrypt the canvas. If the receiving end doesn't decrypt it, the canvas is gonna be random noise.
(This part I'm really unsure about) Due to each client having a different key to encrypt and decrypt, this essentially allows others to track a certain user.
This is already part of my intro