https://www.youtube.com/watch?v=BKkg5s9Jv3kIn OpenID a shared secret is being established between the Relying Party and the OpenID Provider using the Diffie-Hellman Key Exchange and this is used to sign all the messages flow between two parties.
Following is a nice video on Diffie-Hellman Key Exchange, from YouTube.
Following is a nice video on Diffie-Hellman Key Exchange, from YouTube.