Various example embodiments are disclosed relating to sending and processing messages in relay networks. There is a plurality of reflective patterns at the bottom surface of the guiding element. The video data for the comparison pixel blocks from the reference video frame is stored as texture map values in the texture cache of the rendering pipeline. The verification information is supplied to a certification authority, which generates based at least in part on the first public key and the verification information a second public key having a corresponding second secret key, and generates a certificate based at least in part on the second public key. The centralized backup system ensures the reliability of the non-local systems and is able to allocate resources flexibly to meet the requirement of the tasks of system in each different location by centralized deployment and centralized management of backup systems in all locations. Then the image data control unit reads out the image data from the line memory.