Securely transporting data across a data diode for secured process control communications

Securely transporting data across a unidirectional data diode interconnecting a process plant to a remote system includes provisioning, using join key material, a sending device at the plant end of the diode with a receiving device at the remote end. The join key material is used to securely share network key material that is used to encrypt/decrypt messages or packets that are transported across the diode and whose payload includes plant-updated or re-set generated data. The shared network key material is recurrently using the join key material, and the recurrence interval may be based on a tolerance for lost data or other characteristic of an application, service, or consumer of plant data at the remote system.