A set of redundant industrial control system communications/control modules includes at least a first communications/control module and a second communications/control module. The first and second communications/control modules are configured to perform an authentication sequence including: transmitting a request datagram from the first communications/control module to the second communications/control module, the request datagram including a first nonce, a first device authentication key certificate, and a first identity attribute certificate; transmitting a response datagram from the second communications/control module to the first communications/control module, the response datagram including a second nonce, a first signature associated with the first and second nonces, a second device authentication key certificate, and a second identity attribute certificate; and transmitting an authentication datagram from the first communications/control module to the second communications/control module when the response datagram is valid, the authentication datagram including a second signature associated with the first and second nonces.