A games machine includes a video display screen with a transparent front screen in front and a token passage between display screen and front screen. Based on the determined edge number, a plurality of textual blocks are determined out of the plurality of blocks in the digital image and the corresponding textual areas may be extracted from the digital image, so that the textual area and a continuous pictorial area in the digital image may be processed separately. The verification of the certificate’s validity by the relying party is unnecessary, as the signature could not have been created had the certificate been invalid.