> By probing the GPU memory allocation repeatedly, we can detect the pattern of user typing (which typically causes re-rending of the textbox or similar structure animating the characters).

I guess I’m a tiny bit surprised that the browsers are de-allocating and re-allocating memory for the re-render of the text box elements, since they don’t change size. Presumably this would be texture memory? Does anyone here know precisely what’s happening there, and whether a render-to-texture won’t work for some reason? Is it normal for browsers to allocate memory for all element repaints, or is this something unique to text typing or font handling?

The paper mentioned some mitigation avenues from the GPU’s perspective, but there are easy mitigations from the browser side here too. Given their interest in security, it seems reasonable for browsers to move on easy mitigations without waiting for changes to the GPU API.

Rate limiting password fields in the browser, and avoiding GPU memory allocations while the user is only typing into a small text box element would remove the ability to do timing attacks on passwords. Individual websites can even do these things if they’re worried about it.