Two-Level QR Code for Private Message Sharing and Document Authentication

Abstract

International audienceThe quick response (QR) code was designed for storage information and high-speed reading applications. In this paper, we present a new rich QR code that has two storage levels and can be used for document authentication. This new rich QR code, named two-level QR code, has public and private storage levels. The public level is the same as the standard QR code storage level; therefore, it is readable by any classical QR code application. The private level is constructed by replacing the black modules by specific textured patterns. It consists of information encoded using q-ary code with an error correction capacity. This allows us not only to increase the storage capacity of the QR code, but also to distinguish the original document from a copy. This authentication is due to the sensitivity of the used patterns to the print-and-scan (P&S) process. The pattern recognition method that we use to read the second-level information can be used both in a private message sharing and in an authentication scenario. It is based on maximizing the correlation values between P&S degraded patterns and reference patterns. The storage capacity can be significantly improved by increasing the code alphabet q or by increasing the textured pattern size. The experimental results show a perfect restoration of private information. It also highlights the possibility of using this new rich QR code for document authentication

A Novel Three-Layer QR Code Based on Secret Sharing Scheme and Liner Code

“…e time complexity of [2], where an optical encryption was used, was decided by parameter λ. Based on information hiding technology, [5,8,16,20] combined the characteristics of the QR code to embed sensitive information. Among them, the main operation of [8] was based on hash function, whose computational complexity is O(N 2 ).…”

“…Among them, the main operation of [8] was based on hash function, whose computational complexity is O(N 2 ). e main operation of [5] focused on ECC decryption, while the operations in [16] were all addition and modulo operations, which led to a low computational complexity as O(N). Reference [23] was a secret hiding scheme by improving exploiting modi cation direction to protect the private message in QR code with the computational complexity as O(N).…”

“…For the sender, m, D, H, and b are all available, so they can calculate m q×1 ′ by m q×1 ′ � m q×1 ⊕ D q×n × b n×1 . Since there are unchangeable elements in b, which means the modified vector is 0 at the corresponding position, the corresponding column vector in D has no effect on the result of equation (5). Delete the n-k column vectors in D to obtain the submatrices H q×k ; then, Equation (5) can be transformed into…”

“…In addition, by doing the same clipping operation for the three-layer QR code generated in Ref. [5,8,16], the strong robustness of the scheme is highlighted. Among them, the carrier QR code version adopted in Ref.…”

“…In order to improve the accuracy of the extraction, the Hamming code was used to correct errors. Tkachenko et al [5] designed the two-level QR code based on machine vision and selected a unit that replaced the black module of the QR code from several pattern recognition units according to the secret scrambling sequence to achieve two-level storage of information. Based on the error correction mechanism of QR code, Chiang et al [6] used wet paper code to embed secret information into the carrier image to achieve blind extraction of secret information.…”