Optical Fragile Watermarking With Visual Cryptography And QR Code

As digital network technology continues to develop,the sharing and transmission of digital images becomes easier and faster,while image processing techniques become more powerful,making it easy to edit and modify digital images.As a result,there is a growing concern for the authenticity and integrity of images.Particularly in areas such as law,medicine,journalism and commerce,there is a need to authenticate transmitted digital images to determine whether their content has been altered,falsified or specially manipulated.Image authentication techniques for digital watermarking can provide secure authentication of digital images.Among them,fragile digital watermarking technology has become a key technology for authenticating the authenticity and integrity of images due to the inherent sensitivity of its algorithm to image tampering.Once proposed,vulnerable watermarking techniques have been widely studied by scholars at home and abroad.Nowadays,enhancing the security of authentication watermark is the key to promote the development of digital image authentication technology.Optical information security technology is gaining more and more attention thanks to the advantages of high-speed propagation and parallel processing capability of light,as well as high design freedom.This thesis focuses on the application of visual cryptography and QR code technology in optical information security,and achieves complementary advantages through the combination of technologies to achieve an optical information security processing method that is secure,highly concealable,and simple and easy to operate.The main research work of the thesis is as follows:(1)An optical concealment system based on visual cryptography is proposed,and simulation is used to verify the effectiveness and feasibility of the system.The research results show that the designed system has high security and good imperceptibility at the same time.(2)An optical encryption system based on visual cipher and QR code is designed to further extend the application scope of visual cipher and QR code technology.The system uses a double random phase encryption method based on a 4-f system as a framework to combine visual ciphers with QR codes,using QR codes as a powerful carrier of information,and using a visual cryptography scheme to extend the encoding of QR codes generated in plaintext,increasing the diversity of system keys.Following this,the visual key is further encrypted using phase coding techniques,which solves the deficiency of poor ciphertext concealment in traditional visual cryptography and enables the security of the encryption system to be substantially improved.(3)An optically fragile watermarking system incorporating visual ciphers and QR codes is designed for image authenticity and integrity detection.Experimental results show that the system not only effectively resolves the conflict between imperceptibility and watermark extraction quality,but also detects common attacks with high sensitivity and enables good detection and localisation of tampered regions.