Visual cryptography

About: Visual cryptography is a research topic. Over the lifetime, 1724 publications have been published within this topic receiving 25300 citations.

Preserving privacy for video surveillance via visual cryptography

Abstract: The video surveillance widely installed in public areas poses a significant threat to the privacy. This paper proposes a new privacy preserving method via the Generalized Random-Grid based Visual Cryptography Scheme (GRG-based VCS). We first separate the foreground from the background for each video frame. These foreground pixels contain the most important information that needs to be protected. Every foreground area is encrypted into two shares based on GRG-based VCS. One share is taken as the foreground, and the other one is embedded into another frame with random selection. The content of foreground can only be recovered when these two shares are got together. The performance evaluation on several surveillance scenarios demonstrates that our proposed method can effectively protect sensitive privacy information in surveillance videos.

A new non-expansion visual cryptography scheme with high quality of recovered image

Abstract: In the traditional visual cryptography scheme, a secret pixel will be encoded into a block, causing the size of recovered image is larger than the original one. Thus, later studies attempt to improve these shortcomings, distortion of the recover image and a higher transmission cost. This paper proposes a visual secret sharing (VSS) scheme without expansion, and gets a better recovered result than other schemes due to the consideration of black pixels' distribution.

Applying Visual Cryptography to Enhance Text Captchas

Abstract: Nowadays, lots of applications and websites utilize text-based captchas to partially protect the authentication mechanism. However, in recent years, different ways have been exploited to automatically recognize text-based captchas especially deep learning-based ways, such as, convolutional neural network (CNN). Thus, we have to enhance the text captchas design. In this paper, using the features of the randomness for each encoding process in visual cryptography (VC) and the visual recognizability with naked human eyes, VC is applied to design and enhance text-based captcha. Experimental results using two typical deep learning-based attack models indicate the effectiveness of the designed method. By using our designed VC-enhanced text-based captcha (VCETC), the recognition rate is in some degree decreased.

Authentication Mechanism for Secret Sharing Using Boolean Operation

Abstract: A lossless image secret sharing using a simple Boolean operation is proposed The concept of visual cryptography in the secret sharing scheme is used to redesign a lossless secret sharing scheme To ensure that the reconstructed image is the true secret image, an authentication mechanism is imported into the proposed scheme to verify whether the shadows are authentic before reconstructing the secret image The proposed scheme delivers much more effective performance than Chen and Wu's scheme

Threshold Visual Cryptography Schemes With Tagged Shares

Abstract: The appearance of shares encoded by traditional visual cryptography is not easy to distinguish and meaningless. It means the shares cannot be managed efficiently nor user-friendly. A tagged visual cryptography scheme (TVCS) provides additional tag images for the shares and decodes the tag images by folding up a single tagged share. A TVCS allows users to efficiently manage shares and greatly increases the user-friendliness of the shares. Previous researches have focused on codebook-based and random-grid-based TVCS approaches, but the visual qualities of recovered secret images and tag images can still be improved. Therefore, this study aims to provide better visual quality of recovered images by improving on previous methods. Moreover, the proposed approach supports adjustable visual qualities of recovered secret images and tag images. In this study, we theoretically analyze the performances of the proposed approach and then demonstrate implementation of the approach.