Covert Communication via the QR Code Image by a Data Hiding Technique Based on Module Shape Adjustments

A novel data hiding method for covert communication via the QR code image based on adjustments of the shapes of the QR code modules using image processing techniques is proposed. A module block consisting of two module pairs is taken as the unit for message-bit embedding by adjusting the vertical and horizontal internal boundaries in the module pairs. Eliminations of the resulting boundary line zigzaggedness and irregular overlapping and holing phenomena in the module block are also carried out. The resulting stego-image with secret bits embedded can be scanned by a barcode reader to obtain the facial data recorded in the QR code while a program implementing the message extraction process of the proposed method can process the stego-image to extract the hidden secret message. Good experimental results, tests of stego-image readability by QR code scanners and resistance to noise attacks, and a comparison with other methods from the viewpoint of data embedding rate show the feasibility and superiority of the proposed method for real covert communication applications.