Privacy

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the encryption keys, why can't the government just sneak on them? (lemmy.dbzer0.com)

submitted 10 months ago* (last edited 10 months ago) by [email protected] to c/[email protected]

33 comments fedilink hide all child comments

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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[–] [email protected] 64 points 10 months ago* (last edited 10 months ago) (11 children)

SSL/TLS, the "S" in HTTPS, and other network encryption protocols such as SSH, use a technique called a Diffie-Hellman key exchange. 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).

You and Youtube only ever exchange the public halves of your respective key pairs. If someone snoops on the key exchange all they can do is insert spoofed messages, not decrypt real ones.

Moreover, the keypairs are generated on the fly for each new session rather than reused. This means that even a future compromise of youtube won't unlock old sessions. This is a concept called forward secrecy.

Message spoofing is prevented by digital signatures. These also use the Diffie-Hellman principle of pairs of public/private keys, but use separate longer-term key pairs than those used with encryption. The public half of youtube's signing key, as presented by the server when you connect to it, has to be digitally signed by a well-known public authority whose public signing key was shipped with your web browser.

[–] [email protected] 9 points 10 months ago* (last edited 10 months ago) (10 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??

[–] matthewc 16 points 10 months ago (1 children)

Your computer generates two keys. One to encrypt a message. One to decrypt the message. The encrypt key is public. The decrypt key is private. Your computer shares the public key with YouTube. The private key is never shared.

YouTube does the same thing for your computer.

Your computer will have YouTube’s public key and your computer’s private key..

Your computer will be able to encrypt messages to send to YouTube that only YouTube will be able to decrypt. Even your computer will not be able to decrypt these messages after it has encrypted them using YouTube’s public key.

Since the decryption keys are never shared they can’t be snooped. That is why it is only possible for an attacker to encrypt new messages but not read any messages from either sender.

[–] [email protected] 3 points 10 months ago

Good description of asymmetric cryptography!

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