Diffie-Hellman Key Exchange

Introduction:

The Diffie-Hellman Key Exchange is a cryptographic method that allows two parties to establish a shared secret over an insecure channel. While the protocol allows secure key exchange, it is vulnerable to a Man-in-the-Middle (MITM) attack if the identities of the communicating parties are not authenticated.

How Diffie-Hellman Works (Briefly):

Let:

• g be a public base (generator),

• p be a large prime number (public modulus),

• Alice chooses a private key a, computes A = g^a mod p,

• Bob chooses a private key b, computes B = g^b mod p.

Then they exchange A and B and compute the shared key:

• Alice computes K = B^a mod p,

• Bob computes K = A^b mod p.

Since g^(ab) mod p = g^(ba) mod p, both arrive at the same shared key.