Lets someone opens https://foo.com and saves the page using "save page as".

Is there any way to prove later that the locally saved files have not been altered assuming that we trust the server public key?

Since there was a certified public key when the page was downloaded, it should be possible in theory. Is it implemented in any standard?

  • While not exactly a duplicate the questions I've linked to actually ask about even weaker conditions, i.e. prove that the server has sent the data at all (no matter at which time) or that the data were sent over HTTPS. And even these much weaker problems cannot be solved by HTTPS. Given that your problem requires that these simpler problems got solved already it cannot be solved either by HTTPS alone. To solve the problems just trusting the servers key is not sufficient. – Steffen Ullrich Mar 2 at 7:01