Honest Public Values - A Middle Person Makes Two Secrets

Alice and Bob have ordinary DH public values, but those values are not yet tied to identity.

highlighted = computed this step

Honest DH sends public values

Alice would publish A=8 and Bob would publish B=19.

A=8\quad B=19

The arithmetic does not say who sent the public value. Without authentication, a middle person can swap the value in transit.

\text{public value needs identity}

If Alice and Bob used each other's real public values, the shared value would be 2.

\text{honest shared}=2

The honest public values are visible, but the transcript still needs a way to prove whose value arrived.

\text{identity is missing}