Implementation of a Digital Signature in Backward-Compatible QR Codes Using Subcell Division and Double Encoding

The current version of a quick response (QR) code can be easily created by anyone and then used to perform an impersonation or forgery. As one countermeasure against this, methods that implement a digital signature algorithm for QR codes have been proposed. However, many of these methods store application data and the digital signature in the same area. From the viewpoint of compatibility, it is necessary for a digital signature to be stored in an area that is independent of the application data. Therefore, we propose a method of dividing a black cell into four subcells and implementing an elliptic curve digital signature algorithm using double encoding.