Questions tagged [diffie-hellman]

The Diffie–Hellman key agreement is an anonymous, non-authenticated key-agreement protocol.

588 questions
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How to solve the Diffie-Hellman problem if $g$ is unknown?

I am trying to solve the Diffie-Hellman problem modulo a composite number $N$, which I have factored. In this question, it was answered how to deal with such a situation. But how can I solve the ...
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Extracting Private Keys in Diffie Hellman

I know that the security of Diffie Hellman Key Exchange depends upon the discrete logarithm problem, but is it possible to extract the private keys if we know more? Say that in addition to modulus ($q$...
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ClientKeyExchange in static DH

I am confused about the content of ClientKeyExchange in case if the key-exchange is static DH. The TLS 1.2 standard says under section 7.4.7 in https://tools.ietf.org/html/rfc5246#page-57: If the ...
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How to use ECDH keypairs algorithm for encryption and decryption same like RSA keypairs without key agreement?

Is it possible to use ECDH key pairs (Public and private keys) for encryption and decryption like RSA key pairs in encryption and decryption. Say for example, if i have RSA key pairs then i could do ...
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Groups for which DDH is easy but CDH is hard

For prime p, is $\mathbb{Z}^{*}_{p}$ a group for which the Decision Diffie-Hellman problem is easy (because one can compute the Legendre symbol of ($g^{ab}$) while CDH is thought to be hard? Of course,...
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where does the prime number taken in DH algorithm in IPSEC

I am studying & configuring IPSEC ikev1 and in between i am analysing the wireshark captures. I am using the linux kernel for TCP/IP stack and user-space i took ipsec-tools. In the first two ...
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The site badssl.com provides examples of bad (red icon) and good (green icon) uses of TLS for the purpose of testing TLS implementations. I'm a bit confused by the test called dh-composite. This ...
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Bob has an EC key pair. How can he receive a small integer in the least compute intensive way?

Alice wishes to send Bob a number $n$ between 0 and 255. Bob has a private, public EC key pair $(b, B)$ where $B = bG$ and $G$ is an already agreed upon base point on the ed25519 curve. Alice could ...
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Is ECDH(E) Key Exchange FIPS 140-2 compliant?

We have read dozens of documents now - some that contradict each other - and cannot find a solid source of truth. Does FIPS 140-2 compliance allow for the use of elliptic curve cryptography as a key ...
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DH Key Exchange Protocol (one-out-of two)

Now given this problem, for part 1) I have solved it as follows, (I hope I am correct). The basic idea is this: I Have two prime numbers g and p and I tell you what they are. You choose a secret ...
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What's the difference between RSA and Diffie-Hellman? [duplicate]

I've been reading on a lot of websites that same thing: RSA is for communication using the public and private key for both the server and client, where Diffie-Hellman is just for exchanging the same ...
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Computational Diffie-Hellman problem

From here, The Computational Diffie-Hellman problem: Given $y_1 = g^{x_1}$ and $y_2 = g^{x_2}$ (but not $x_1$ and $x_2$), find $y = g^{x_1·x_2}$. What happens if I knew one of the $x_1$, would it ...