this post was submitted on 21 Jan 2024
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Privacy

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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!

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[–] zaknenou@lemmy.dbzer0.com 6 points 9 months ago* (last edited 9 months ago) (8 children)

this is very detailed answer thank you. however I face an ambiguity regarding this:

This is a mode of cryptography where each side generates two keys: a public half and a private half. Anything encrypted with the public half is only decryptable by the associated private half (and vice versa).

How can this private half be something that I know, Youtube knows but impossible for the snooper to our communication to know??

[–] Darkassassin07@lemmy.ca 4 points 9 months ago* (last edited 9 months ago) (7 children)

Youtube never knows the private half of your key pair. That never leaves your system.

Anything encrypted with the private half can only be decrypted with the public half, and anything encrypted with the public half can only be decrypted with the private half. These halves are known as the public key and the private key. Each side of the connection generates their own key pairs.

We both generate a set of keys, and exchange the public halves with each other. I then want to send you a message: I first encrypt it using my private key, I then encrypt it again using your public key and send that to you.

In order to read that message, you first decrypt it using your private key. This ensures the message was intended for you and wasn't modified in transit, as you are the only one with access to that private key and only its matching public key could have been used to encrypt that layer.

You then decrypt it a second time using my public key. As I'm the only one with access to my own private key, you can be sure the message was sent by me.

As long as that resulted in a readable message; You've now verified who sent the message, that it was intended for you, and that the contents have not been modified or read in transit.

All this, including the key exchange is handled for you by the https (tls) protocol every time you connect to a website. Each of the messages sent between you and the site are encrypted in this manner.

[–] zaknenou@lemmy.dbzer0.com 3 points 9 months ago (2 children)

so you can encrypt a message with my public key but you cannot decrypt it afterward ??

[–] deluxeparrot@thelemmy.club 4 points 9 months ago* (last edited 9 months ago)

The best way I find to think about it is a padlocked box.

The public key is a box with an open padlock on it. I can give it to anyone. If someone puts a message inside the box they can lock the padlock, but they don't have the key to open it again.

I keep the key private. If someone sends me a locked box that has my padlock on it, only I have the key to open it and read the message.

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