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

learn more… | top users | synonyms

2
votes
0answers
105 views

Difference between “ECDH with cofactor key” and “ECDH without cofactor key”?

I need to use “ECDH with a cofactor key” for generating symmetric key. I have a fair idea on how ECDH works, but I don’t understand the cofactor part. What is the difference between ”ECDH with a ...
1
vote
1answer
148 views

Use ElGamal to solve Diffie-Hellman problem

Say we are able to decrypt a Elgamal ciphertext $c$ using only the public key. Apparantly it is now possible to solve the Diffie-Hellman problem (given $g^a, g^b$ calculate $g^{ab}$). How? I know how ...
0
votes
1answer
352 views

Problem with Python Implementation of Key Exchange part OTR Protocol

Being new to software development and crypto in general, I thought I would write a simple p2p encrypted chat app using the otr protocol detailed here: https://otr.cypherpunks.ca/Protocol-v3-4.0.0.html ...
5
votes
1answer
122 views

Condensed ElGamal + AES

In normal ElGamal encryption, the encrypted message is a pair (gb, gabM) - that is, the actual "encryption" is simply multiplication by the shared secret ...
1
vote
1answer
84 views

Public Key Cryptography: Diffie-Hellman Key Exchange

Please watch this video it's very short. If you already know cryptography and really good at it please start from 3:51. I didn't understand the step at 4:39, can someone here to explain? Why is ...
1
vote
1answer
146 views

DH “prime size” security in OpenSSL

There's a program that uses the following OpenSSL function... DH_generate_parameters(256, 5, NULL, NULL) ...to create DH parameters which are later used for ...
2
votes
1answer
67 views

TLS - sharing 1792 bits of unidirectional keys

I've just watched a video on the TLS protocol and learnt that it uses unidirectional keys (meaning keys for both sides, from browser to server and from server to browser). Given that the server uses ...
7
votes
1answer
239 views

curve25519 weak points for contributory behaviour

The Diffie-Hellman on curve25519 is usually calculated using the base point $(9,…)$ which induces a cyclic subgroup of $G:=\{\infty\}\cup(E(F_{p^2})\cap(F_p\times F_p))$ with index 8, i.e. there is a ...