How to track the opening of word files through a digital signature system?

Question

Data protection

Once I read a post, it seems, on Habré, which said that there is a mechanism that can track the opening of word documents through a system of digital signatures. It seems that the idea was to sign the file through some left certifying authority located on the Internet, and word, when opening the file, would have to refer to it to check if everything was valid. There everything was connected through COM OS Windows, it seems ... But! I can’t find this article in any way, although I’ve been looking for a long time ... Maybe someone is aware of this case, or is it just that my hands are straighter than mine?