Attacks on Steganographic Systems and Watermarking

Tato práce se zabývá steganalýzou, neboli detekcí steganografie, a dále pak útoky na di- gitální vodoznaky, jejichž úlohou je zneplatnění vodoznaků. V práci je navržena a imple- mentována aplikace, sloužící na detekci stegogramů. Aplikace se zabývá hlavně obrázky, vytvářenými metodou substituce nejméně významných bitů programem QuickStego. Spo- lehlivou detekci zajišťuje navržená metóda, která dekóduje informace vložené do obrázku, a vyhledává specifická data vkládaná programem QuickStego. V závěru práce jsou prováděny experimenty na vzorce obrázků, které potvrzují možnost detekovat stegogramy.This thesis focuses on steganalysis, which is detection of steganography, and then on at- tacks on digital watermarking, which aim to invalidate watermarks. The application for stegograms detection is designed and implemented in this thesis. The application focuses on the images, produced by substitution of the least significant bits in QuickStego program. Reliable detection is insured by the designed method, which decodes information embedded in the image, and searches for specific data embedded by the program QuickStego. In the end of the thesis, few experiments are conducted on the sample images, which confirm the ability of detecting stegograms.

Steganalytic Methods for the Detection of Histogram Shifting Data Hiding Schemes

Peer-reviewedIn this paper, several steganalytic techniques designed to detect the existence of hidden messages using histogram shifting schemes are presented. Firstly, three techniques to identify specific histogram shifting data hiding schemes, based on detectable visible alterations on the histogram or abnormal statistical distributions, are suggested. Afterwards, a general technique capable of detecting all the analyzed histogram shifting data hiding methods is suggested. This technique is based on the effect of histogram shifting methods on the ¿volatility¿ of the histogram of the difference image. The different behavior of volatility whenever new data are hidden makes it possible to identify stego and cover images

АТАКИ НА СУЧАСНІ СТЕГАНОГРАФІЧНІ СИСТЕМИ І МЕТОДИ ЗАХИСТУ

In the article attacks on steganographic systems (including digital watermarking systems) have been investigated. Classification of attacks based on the filled container has been suggested. These attacks do not change the container with hidden information and this is their main peculiarity. In particular, attacks that have analogs in cryptanalysis have been analyzed. These are attacks based on known filled container or embedded message and also selected filled container or selected embedded message. Attacks on steganographic systems of the intellectual property, whose purpose is the destruction or removal of a digital watermark have been also analized in the article. Methods of protection against geometric attacks, cryptographic attacks, attacks on removing digital watermark andattacks against protocol, used for embedding a digital watermark have been sugested.Проведено дослідження атак на стеганографічні системи, зокрема системи цифрових водяних знаків. Здійснено класифікацію атак на основі заповненого контейнера. Особливістю таких атак є те, що вони не змінюють контейнера з прихованою інформацією. Крім того, проаналізовано атаки, які мають аналоги в криптоаналізі, а саме атаки на основі відомого заповненого контейнера або відомого вбудованого повідомлення, вибраного заповненого контейнера або вибраного вбудованого повідомлення. Також розглянуто особливості атак на стеганографічні системи інтелектуальної власності, метою яких є руйнування або видалення цифрового водяного знака. Зокрема проаналізовано і наведено рекомендації із використання методів захисту від геометричних, криптографічних атак, а також атак на видалення цифрового водяного знака і проти використаного для вбудовування цифрового водяного знака протоколу

On the Removal of Steganographic Content from Images

Steganography is primarily used for the covert transmission of information even though the purpose can be legitimate or malicious. The primary purpose of this work is to build a firewall which will thwart this transmission. This will be achieved by radiometric and geometric operations. These operations will degrade the quality of cover image. However these can be restored to some extent by a deconvolution operation. The finally deconvolved image is subjected to steganalysis to verify the absence of stego content. Experimental results showed that PSNR and SSIM values are between 35 dB - 45 dB and 0.96, respectively which are above the acceptable range. Our method can suppress the stego content to large extent irrespective of embedding algorithm in spatial and transform domain. We verified by using RS steganalysis, difference image histogram and chi-square attack, that 95 per cent of the stego content embedded in the spatial domain was removed by our showering techniques. We also verified that 100 per cent of the stego content was removed in the transform domain with PSNR 30 dB - 45 dB and SSIM between 0.67-0.99. Percentage of stego removed in both domains was measured by using bit error rate and first order Markov feature

Universal Image Steganalytic Method

In the paper we introduce a new universal steganalytic method in JPEG file format that is detecting well-known and also newly developed steganographic methods. The steganalytic model is trained by MHF-DZ steganographic algorithm previously designed by the same authors. The calibration technique with the Feature Based Steganalysis (FBS) was employed in order to identify statistical changes caused by embedding a secret data into original image. The steganalyzer concept utilizes Support Vector Machine (SVM) classification for training a model that is later used by the same steganalyzer in order to identify between a clean (cover) and steganographic image. The aim of the paper was to analyze the variety in accuracy of detection results (ACR) while detecting testing steganographic algorithms as F5, Outguess, Model Based Steganography without deblocking, JP Hide&Seek which represent the generally used steganographic tools. The comparison of four feature vectors with different lengths FBS (22), FBS (66) FBS(274) and FBS(285) shows promising results of proposed universal steganalytic method comparing to binary methods