using https for websites ensures that the communication is encrypted and comes from and goes to the right server. BUT https is really slow compared to http, it also breaks the http cache protocol.
Sometimes it's enough to ensure the user is on the right domain and the content was not modified during the connection. So what i don't understand is why isn't there a way to make digital sign the web content an send the signiture (or hash) via http header, so the browser can validate the content. The certificate could be made available at a known place or by an additional header field. The resulting Protocol would be compatible with almost every HTTP stuff like caching, proxies, and browsers( if the browser does not understand the header it can ignore it. a new browser could show if the site is valid or not).
So where here is the question: Was this topic discussed before? Or is there a RFC or something that can sign web pages already?