Control systems for unmanned vehicles

A control system (100, Fig. 1) and method for an unmanned vehicle (10, Fig. 1) comprises a control processing unit (102, Fig. 1) which receives input signals from sensors (101, Fig. 1) and supplies output signals to actuators (103, Fig. 1). The processing unit comprises processing modules 110, which may possess double or triple modular redundancy, arranged in stages 120. In the first stage 120A multiple modules 110A, 110B, 110C produce equivalent payload data when operating correctly, and each module includes a cryptography unit (140, Fig. 4) that generates cryptographically signed messages (800, Fig. 8) containing the payload data. The cryptographic implementation may be public key cryptography, identity based encryption or symmetric encryption. Hash-based message authentication codes and non-repudiation may also be used. The messages may be passed in one direction from one stage to the next in message streams via communications networks. Each communications network may be a bus. In each module 110D, 110E, 110F of the second stage 120B a voting cryptography unit (130, Fig. 4) applies voting logic to the messages to derive validated payload data for use by the respective module 110D, 110E, 110F of the second stage.