I believe this blog post http://blog.martin-graesslin.com/blog/2015/01/why-screen-lockers-on-x11-cannot-be-secure/ http://blog.martin-graesslin.com/blog/2015/01

I believe this blog post http://blog.martin-graesslin.com/blog/2015/01/why-screen-lockers-on-x11-cannot-be-secure/ http://blog.martin-graesslin.com/blog/2015/01/why-screen-loc... is relevant to the conversation and the key logger part (but I am out of my league to comment about it).