US Patent 7735120 Server computer issued credential authentication

A method for authenticating computers is disclosed. The method comprises issuing a credential from a first computer to a second computer. When the second computer authenticates to the first computer, the second computer transmits the credential and a first challenge to the first computer. The first computer determines whether the credential is valid, computes a first response to the first challenge, and generates a second challenge. The first computer transmits the first response and the second challenge to the second computer. The second computer determines whether the first response is valid and computes a second response to the second challenge. The second computer transmits the second response to the first computer in order to verify and authenticate the computers.