A QR Symbol with ECDSA for Both Public and Secret Areas using Rhombic Sub-cells

QR codes have a public data area that anyone can read. However, if there was a secret data area that could be read with only a specific reader, their application range could be greatly expanded. Anyone can create a QR code, so QR codes are easy to spoof or forge. A potential countermeasure is to implement a digital signature in the symbol. For a QR code to be able to safely transfer both secret and public data, it needs three independent data areas: a public data area, a secret data area, and a digital signature area. To meet this requirement, we propose using a QR symbol with a rhombic sub-cell structure that has a central sub-cell part and a lattice sub-cell part. Public data is stored in the central sub-cell part, and a digital signature is stored in the lattice sub-cell part. Secret data is encrypted using the recipient’s elliptic function public key and stored in a data area created using double encoding. A digital signature is created that covers both the public data and encrypted secret data, making it possible to safely transfer secret data in addition to public data.