Diffie–Hellman Key Exchange

Building a shared secret in plain sight — explained with paint

Alice

Secret color
private

Her mix
common + red

Shared secret

PUBLIC CHANNEL — everyone can see this

Common paint
agreed in public

Alice → Bob

Bob → Alice

Eve (eavesdropper)

Bob

Secret color
private

His mix
common + teal

Shared secret

Step 1 / 6

Mixing paint is easy — un-mixing it is practically impossible. That one-way property is what keeps the secret safe.