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Cryptology Academy · Lesson

Diffie-Hellman Key Exchange Math

Step through the DH protocol and the discrete-log hardness assumption.

Welcome

In this lesson we trace the Diffie-Hellman key exchange step by step, from the public parameters through Alice and Bob's private exponents to the shared secret.

Public Parameters

Alice and Bob agree publicly on: - p: a large prime (2048+ bits in production) - g: a generator of Z*p (usually g=2 or g=5) Eve can see p and g. Knowing them does NOT break the protocol.

All lessons in this course

  1. The Key Distribution Problem
  2. Diffie-Hellman Key Exchange Math
  3. ECDH: Elliptic Curves for Key Exchange
  4. Forward Secrecy & Ephemeral Key Exchange
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