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#Ethereal vs ephemeral generator

In a static exchange usually both parties always reuse their private keys, which implies that if they re-run the Diffie-Hellman exchange more than once with each other they always get the same shared secret $K$. If so, does static DH refer to exchanges between the same two parties? Then when you shutdown your computer it will "forget" the resulting shared secret $K$ and tomorrow when you connect to Stack Exchange again, it will have to run another Diffie-Hellman exchange. In the context of the internet this usually means that if you connect to, say, Stack Exchange today it will run a Diffie-Hellman exchange.

This happens whenever either a party feels like it or a party has forgotten the resulting shared secret from the last execution. What is considered an exchange? A session of information exchanging between to parties?Īn exchange is an execution of the Diffie-Hellman protocol. Similarly, $A=g^a\bmod p$ and $B=g^b\bmod p$ are also called the "public keys". ThanksĪre "private keys" in the context of diffie-hellman refer to the private $a$ and $b$ that Alice and bob privately select respectively? It'll be great if someone could clarify this whole subject.

If not so, considering that, seemingly, using static DH also requires the use of the same $g$ and $p$, how does using static DH will always generate the same $K$?.

If so, does static DH refer to exchanges between the same two parties?.

What is considered an exchange? A session of information exchanging between to parties?.

Now, what I don't understand here is, what does it mean that "static DH exchanges always use the same Diffie-Hellman private keys."? I mean: So, each time the same parties do a DH key exchange, they end up with the same shared secret.įirst to verify some issue: Are "private keys" in the context of diffie-hellman refer to the private $a$ and $b$ that Alice and bob privately select respectively? I'll assume they do, if not - correct me please. The explanations I see on the web are all sorts of:Įphemeral Diffie-Hellman (DHE in the context of TLS) differs from the static Diffie-Hellman (DH) in the way that static Diffie-Hellman key exchanges always use the same Diffie-Hellman private keys.

Alice selects a private integer ( $a$) and computes $A=g^a\bmod p$.

Bob selects a private integer ( $b$) and computes $B=g^b \bmod p$.

#Ethereal vs ephemeral generator

Bob and Alice agree publicly on a generator ( $g$) and a prime modulo ( $p$).

Let's briefly recall how diffie-hellman basically works: I feverishly searched the web and couldn't find a clear explanation about what exactly is "Ephemeral diffie-hellman".