Thank you Chapalence for that detailed explanation. Just to be clear, this is he site to use to generate a password:https://satid.sat.gob.mx. You have to follow the procedures, including recording a video with your computer's camera (or I assume phone's). You have to repeat a phrase, which can be long and disappears when you turn on your camera, so write it down if you want (my computer translates automatically so everything was in english). You have to attach an ID, I used a passport, photo and opposing page, so have one ready to upload. If they approve they will email me a password ( I guess) within 5 days. I assume I will enter the password on the other site:https://www.sat.gob.mx and be able to generate my CSF.