Better methods and tools are needed in the fight against child pornography. This thesis presents amethod for file type categorisation of unknown data fragments, a method for reassembly of JPEGfragments, and the requirements put on an artificial JPEG header for viewing reassembled images.To enable empirical evaluation of the methods a number of tools based on the methods have been<lb...

In this paper, we propose a semi-fragile watermarking technique that accepts JPEG lossy compression on the watermarked image to a pre-determined quality factor, and rejects malicious attacks. The authenticator can identify the positions of corrupted blocks, and recover them with approximation of the original ones. In addition to JPEG compression, adjustments of the brightness of the image withi...

The first two sections provide some Gauguin-like informational structure: where MPEG came from, what it is, where it is going. The description of related standards bodies is dated when considering younger readers whose main exposure to CCITT is their CRC polynomial. But it was probably helpful at the time. What isn't dated, in fact is remarkably relevant, is the relationship between MPEG and JP...

This paper shows that it is possible to train large and deep convolutional neural networks (CNN) for JPEG compression artifacts reduction, and that such networks can provide significantly better reconstruction quality compared to previously used smaller networks as well as to any other state-of-the-art methods. We were able to train networks with 8 layers in a single step and in relatively shor...

In this article we propose a new fragile watermarking algorithm that provides the means to verify the integrity of JPEG images. We begin by presenting the cryptanalysis of CWSA (Chaotic Watermarking Scheme for the Authentication of JPEG Images), an existing fragile watermarking algorithm. We analyse its weaknesses and we propose a new version that is resistant to those attacks, faster and less ...

A novel image authentication algorithm resisting to JPEG compression is proposed. The authentication watermark is generated based on the stability of relationship of adjacent Contourlet transform coefficients before and after JPEG. According to the random block mapping, the watermark is embedded into the discrete cosine transform (DCT) coefficients of other image blocks. The tampering identific...

Pictures used by GPS devices are usually overly large to be stored as Bit Map, so they are by and large compressed. The common compression method is JPEG; however JPEG assumes that the average color of beginning of each blocks line is usually similar to the average color of end of its preceding blocks line. Many times this assumption is incorrect for GPS picture. This paper suggests a way to ch...

This paper presents a robust image authentication approach that distinguishes malicious attacks from JPEG lossy compression. The authentication procedure calculates the relationships between important DCT coefficients in each pair of DCT blocks and predefined thresholds to form the authentication message, and then embeds the encryption of the authenticated message into other DCT coefficients. T...