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!
I think you’re asking if it’s possible for your government to be a man-in-the-middle? Depending on which government you live under, the answer is likely no but more importantly the answer will always be; it’s not worth their effort to find out what you’re watching.
YouTube’s public key is signed by a certificate authority whose public key (root) is likely installed on your device from the factory. When you connect to YouTube, they send you a certificate chain which your browser will verify against that known root. In effect, it’s information both you and YouTube already share and can’t be tampered with over the wire.
Technically, those signatures can be forged by a well resourced adversary (i.e. a government) with access to the certificate authority through subversion, coercion, etc. At the same time, it’s probably easier to subvert or coerce you or YouTube to reveal what you watch.
Other comments here do a great job pointing to DH key exchange; I’d like to try explaining it with the paint analogy.
You and Youtube need to agree on a “color of paint” (encryption key) without ever sending it over the network.
You and Youtube agree on a common “yellow” in the clear, and you each pick a secret color. Youtube mixes yellow and their secret and sends it to you. This is okay, because un-mixing paint (factoring large prime numbers) is really hard. You add your secret to the mixture, and now you have yellow+Youtube’s secret+your secret.
You mix yellow and your secret and send it to youtube. Youtube adds their secret; now they’ve got yellow+Youtube’s secret+your secret. You both have the final color!
An eavesdropper can’t reconstruct this - everything sent over the network had yellow mixed in, and un-mixing paint can be really hard. Maybe you can guess that green minus yellow is probably blue, but you can’t get close enough to decrypt anything. And what if it’s brown? Is that blue + orange, or is it red + green?
Cryptographers have worked very hard to make the communications secure. I would be more worried about the other end ratting you out - using a relay / proxy / vpn that you trust is a good idea :)
Asymetrical encryption solves this, here is my attempt to do an ELI5:
Adam want’s to send a chat message to Ben, but want to do it securely, so they use a special program on their computers.
When the Adam’s program first reaches out to Ben’s computer, it asks for an unlocked padlock, this is a padlock that can only be unlocked by Ben’s program.
Adam’s program takes the padlock and crafts a new special series of padlocks that only Adam’s program can unlock, which it put’s in a box and locks it with Ben’s padlock.
The box is sent to Ben’s program, the program unlocks the box and creates it’s own special series of padlocks that only Ben’s program can unlock, put them in a box and locks it with Adam’s padlocks.
The box is then sent to Adam’s program, and is unlocked.
This now means that Adam’s program can put messages to Ben in a box, lock the box with one of Ben’s special padlocks and send it on it’s way knowing that only Ben can unlock the box and read the message.
Likewise, Ben can also send messages in boxes locked with Adam’s padlocks and know that only Adam can unlock them and read the message.
Added to this is the fact that messages from Ben can be verified as having used the special padlocks Adam sent to Ben, as else Adam’s special key wouldn’t fit the padlocks given to Ben.
In reality the padlocks are keys to lock a message, and the above text describe a secure key exchange.
Oh! I remember these steps being explained on a youtube video before. So the point is that the padlock (that Adam received on the third paragraph) is like a program on my windows desktop, I can run it (here like Adam uses it to encrypt the date), I can copy it and send it to a friend, but I can’t read the code which is compiled through an unknown language (i.e even if snooper received the padlock he can’t figure out how to unlock it and decrypt the data)?
Yep, if a thrid party gets the padlock they can lock the box, but can’t unlock other boxes
While we’re talking about asymmetric encryption, can someone explain to me why you can’t decrypt information with the same public key that encrypted it? I understand the analogies (locks on a briefcase, unmixing paint, etc), but I can’t “un-analogize” them to understand what’s actually going on. Encryption keys aren’t physical locks or paint. They’re numbers(?). So why can I encrypt something by multiplying by a known public encryption key, but I can’t decrypt it by dividing by that same known public key?
