Approximate thumbnail-preserving encryption based on single-pixel imaging

With the rapid development of smart devices and Internet technology, the volume of visual data stored in the cloud has increased dramatically, posing severe challenges to security and privacy protection. Traditional image encryption methods often produce encrypted images that are difficult to view, preventing users from previewing content in the cloud. Thumbnail-preserving encryption (TPE) enables encrypted images to retain visual features, thereby striking a balance between security and usability. Most thumbnail-preserving encryption schemes employ complex pixel-wise encryption operations, which often suffer from long encryption times, low perceptual quality of the encrypted images, and a high file expansion rate of the encrypted image. This paper proposes an approximate thumbnail-preserving encryption scheme based on single-pixel imaging, referred to as TPE-SPI. The scheme utilizes the bucket signals, speckle patterns, and the pixel values of the target image, along with the relationships among them, to achieve efficient and secure thumbnail-preserving encryption through simple processing of the bucket signals. Compared to other schemes, TPE-SPI offers higher encryption efficiency and better visual quality of the encrypted image, while effectively reducing the file expansion rate of the encrypted image.