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A doubt in encryption (lemmy.ml)

submitted 6 months ago by [email protected] to c/[email protected]

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There’s a server, a client, and a hacker in a network. For encryption, the client and the server need to share their private keys. Wouldn’t the hacker be able to grab those during their transmission and decrypt further messages as they please?

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[–] [email protected] 2 points 6 months ago (2 children)

If you know the private key it is trivial to calculate the public key, but the reverse isn't true

I didn't believe this is true... In public/private key crypto there is no such thing as "private" and "public". They're just a key pair. You choose to make one public by sharing it and the other private by not sharing it.

[–] [email protected] 2 points 6 months ago

It depends on the cryptosystem. The private and public halves of the pair are often not symmetrical and often have overlap.

The parent is likely confused because in most situations the "private key file" will also contain all of the public key. Whether by necessity or for convenience.

[–] [email protected] 1 points 6 months ago

Ok, semantics - for RSA you generate a private key, then derive the public key from that private key, and you could publicly post your private key if you wanted to. "Public" and "private" are just names.