TPEIP: Thumbnail preserving encryption based on sum preserving for image privacy

Image privacy technology is a growing important topic in cloud storage services. User can use the cloud services to browse or manage their own images, however, the user will face the problem of image privacy. Accordingly, the traditional image encryption scheme is a way to ensure the safety of images. However, encrypted images will lose their image usable property when users want to search and browse their own images online without downloading and decrypting them. Marohn et al. designed two thumbnail-preserving-encryption (TPE) methods to balance the image privacy and usability. In this paper, a novel TPEIP method based on sum-preserving-encryption (SPE) is proposed for enhancing the image privacy. SPE can avoid the statement of fail encryption using the approximate TPE method. We also applied formulas to present the correctness of the proposed scheme. The combination of thumbnail and encryption approach allows the user to quickly compare encrypted images using thumbnail. Experimental results show that our proposed method not only retained the same thumbnail appearance before and after encryption but also held the image encryption with sufficiently confidential.