Research On Image Encryption And Security Based On Visual Cryptography

With the increase of data transmission,people have higher requirements for information security.There are many ways to protect data,such as watermark,identity authentication,image hiding and key exchange.These methods hide the secret information in a single carrier.If the hidden information is lost,the secret cannot be recovered.Compared with the traditional cryptosystem,visual cryptography has been transmitting information in the form of shared image.It has strong concealment,high security,and does not need complex mathematical calculation when decrypting.In this paper,three image encryption algorithms are proposed based on visual cryptography,combining information hiding technology,optical processing technology and halftone technology.The main contents are as follows:(1)An image encryption algorithm based on visual cryptography and steganography is implemented.Firstly,the secret image is divided into several bit planes,which are embedded into the RGB component image of the carrier image by using the bit plane coding algorithm until all the bit plane images are embedded,then a steganographic image is obtained.Then the steganographic image is divided into several shared images by visual cryptography scheme.Finally,LSB algorithm is used to hide all the shared images into the envelope images.After two times of data hiding and using visual cryptography scheme to encrypt the image,the security and robustness of the secret image are improved.(2)An QR code visual encryption algorithm based on single pixel imaging is designed.Firstly,the generated QR code is processed into an image with the size of 2i ×2i pixels.Then,the secret image is divided into blocks according to the size of 4 × 4 pixels,and the pixel strength of each block is calculated and recombined.Finally,the secret image is generated into a number of shared images in two-dimensional code mode.When these images are illuminated by multiple groups of the same illumination mode,they are recorded with the same single pixel detector,and the secret image is reconstructed from the recorded sequence.The algorithm uses QR code as the shared image,which is not easy to be detected by attackers,and the shared pixel value cannot be determined after overlay,so it has high security.(3)A halftone image encryption algorithm based on extended visual cryptography scheme is proposed.Firstly,Stucki error diffusion is used to halftone gray images.Then the generated halftone secret images are stored in the halftone sharing images using the extended visual cryptography scheme.Finally,meaningful shared images are obtained.The algorithm is also applied to color image.Firstly,RGB color decomposition is performed on the color secret image and the masked images,and halftone images are generated by Stucki error diffusion algorithm.Then,Otsu is used to get the appropriate threshold to convert the halftone color component into binary image.Finally,the extended visual cryptography scheme is used to generate two meaningful shared images.This method can generate meaningful shared images with high visual quality.Compared with meaningless sharing,meaningful shared images are not easy to be detected by attackers and have higher security.