Biblio

Many portable imaging devices use the operation of "trunc" (rounding towards zero) instead of rounding as the final quantizer for computing DCT coefficients during JPEG compression. We show that this has rather profound consequences for steganography and its detection. In particular, side-informed steganography needs to be redesigned due to the different nature of the rounding error. The steganographic algorithm J-UNIWARD becomes vulnerable to steganalysis with the JPEG rich model and needs to be adjusted for this source. Steganalysis detectors need to be retrained since a steganalyst unaware of the existence of the trunc quantizer will experience 100% false alarm.

The Internet of Things (IoT) technology is being utilized in endless applications nowadays and the security of these applications is of great importance. Image based IoT applications serve a wide variety of fields such as medical application and smart cities. Steganography is a great threat to these applications where adversaries can use the images in these applications to hide malicious messages. Therefore, this paper presents an image steganalysis technique that employs Convolutional Neural Networks (CNN) to detect the infamous JPEG steganography technique: JPEG universal wavelet relative distortion (J-UNIWARD). Several experiments were conducted to determine the breaking point of J-UNIWARD, whether the hiding technique relies on correlation of the images, and the effect of utilizing Discrete Cosine Transform (DCT) on the performance of the CNN. The results of the CNN display that the breaking point of J-UNIWARD is 1.5 (bpnzAC), the correlation of the database affects the detection accuracy, and DCT increases the detection accuracy by 13%.

The paper proposes a method for image content recovery based on digital watermarking. Existing image watermarking systems detect the tampering and can identify the exact positions of tampered regions, but only a few systems can recover the original image content. In this paper, we suggest a method for recovering the regions of interest (ROIs). It embeds the semi-fragile watermark resistant to JPEG compression (for the quality parameter values greater than or equal to the predefined threshold) and such local tamperings as splicing, copy-move, and retouching, whereas is destroyed by any other image modifications. In the experimental part, the performance of the method is shown on the road traffic JPEG images where the ROIs correspond to car license plates. The method is proven to be an efficient tool for recovering the original ROIs and can be integrated into any JPEG semi-fragile watermarking system.

Thumbnail preserving encryption (TPE) was suggested by Wright et al. [Information Hiding & Multimedia Security Workshop 2015] as a way to balance privacy and usability for online image sharing. The idea is to encrypt a plaintext image into a ciphertext image that has roughly the same thumbnail as well as retaining the original image format. At the same time, TPE allows users to take advantage of much of the functionality of online photo management tools, while still providing some level of privacy against the service provider. In this work we present two new approximate TPE encryption schemes. In our schemes, ciphertexts and plaintexts have perceptually similar, but not identical, thumbnails. Our constructions are the first TPE schemes designed to work well with JPEG compression. In addition, we show that they also have provable security guarantees that characterize precisely what information about the plaintext is leaked by the ciphertext image. We empirically evaluate our schemes according to the similarity of plaintext & ciphertext thumbnails, increase in file size under JPEG compression, preservation of perceptual image hashes, among other aspects. We also show how approximate TPE can be an effective tool to thwart inference attacks by machine-learning image classifiers, which have shown to be effective against other image obfuscation techniques.