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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[–] Darkassassin07@lemmy.ca 5 points 10 months ago* (last edited 10 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.

[–] intensely_human@lemm.ee -2 points 10 months ago (3 children)

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.

This is not true. In key pair cryptography, the public key used only for encryption and the private key is used only for decryption.

[–] Darkassassin07@lemmy.ca 2 points 10 months ago (2 children)

As far as I understand a key pair can be used bi-directionally like I'd described. Was I mistaken?

In practice, the private key is usually used to create signatures instead, but I avoided that for simplicity.

[–] chayleaf@lemmy.ml -1 points 10 months ago

no, it isn't bidirectional, public = encrypt, private = decrypt, that's it. You can address a message to multiple recipients though (when using GPG), so often in case of email a message is addressed both to yourself and your recipient, so both you and your recipient have access to message text

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