Encryption in Transit: HTTP to HTTPS

Question

When sending data from a server / device through HTTP, to a destination that is enforced by https, is that data encrypted in transit?

HTTP -> HTTPS

Or does the source and the destination both have to enforce HTTPS?

Answer 1

A protocol is the language between a client and the server. This language might have features including ones related to security. HTTP is basically for browsers requesting web resources from web servers without any encryption, authentication or integrity protection. HTTPS is the same, but one that provides these features (HTTPS is actually HTTP, protected by TLS).

Each tcp connection between components uses one protocol (it's sometimes a little more difficult than that, but let's stick with this, it's good enough for now). In case of web components, it's typically either http or https. Each resource that is downloaded (a page, an image, a javascript file, any resource) is typically downloaded in its own separate connection. Whether that will be http or https depends on how the page references it.

So in practice, if you have a look at a html page that you downloaded over http, it can still reference resources with https urls, in which case those will be downloaded by your browser via https. It can also happen the other way round, a page downloaded over https can reference resources over plain http, but your browser will then warn you.

In short, your question doesn't make sense because you don't "send data through http, to a https destination". If the destination is https, the connection will be using https. In a web application, the page itself can be downloaded via http (in which case the html code and any data embedded in the html itself will not be protected against man-in-the-middle attackers), but it can reference further resources, images, css, javascripts via https, which your browser will then download securely.