disclaimer: I'm just asking to get understanding of the theory behind network traffic encryption, I know this doesn't happen irl most likely.
Let's take https connection for example. I like watching revolutionary things on youtube and do not wish for authorities to know what I am watching, we accept here for the sake of showcase that google won't sell my watch history if asked (LMAO what am I even saying?).
So if I'm not mistaken since youtube has https implemented, our communication is encrypted, the keys are shared only between me and youtube. But when Youtube shares the key with me/my client the first time, is that also encrypted? Wouldn't the same question keep getting answered until there is something unencrypted? I know this is a bit too much unlikely, but if ISP automated the process of gathering keys and decrypting web traffic for a certain site with them for all users, would that work for them?
I'm taking https here as an example, while I have the same question for like VPN.
EDIT: Thank you everybody. I am not a member of this community, but every comment was a golden experience to read!
afaik, most if not all modern browsers and clients in e.g. apps, use Diffie-Hellman key exchange in TLS.
Some Apps go even further and implmement certificate pinning, only allowing a set of specific certificates the server is allowed to "present".
You can only break it by an active Man in the middle attack, presenting your own Diffie-hellman parameters toeachother and signing them with a certificate the client trusts (we can probably assume US agencies have access to some CA keys and can do this)
I dont think this is very feaseable on a large scale as you'd need to intercept every interesting connection, break the handshake, risking detection, and further proxy and process the whole traffic.
Metadata will be more juicy en mass than the content and easier to obtain with less risks.