Mitigation of H.264 and H.265 Video Compression for Reliable PRNU Estimation

The photo-response non-uniformity (PRNU) is a distinctive image sensor characteristic, and an imaging device inadvertently introduces its sensor's PRNU into all media it captures. Therefore, the PRNU can be regarded as a camera fingerprint and used for source attribution. The imaging pipeline in a camera, however, involves various processing steps that are detrimental to PRNU estimation. In the context of photographic images, these challenges are successfully addressed and the method for estimating a sensor's PRNU pattern is well established. However, various additional challenges related to generation of videos remain largely untackled. With this perspective, this work introduces methods to mitigate disruptive effects of widely deployed H.264 and H.265 video compression standards on PRNU estimation. Our approach involves an intervention in the decoding process to eliminate a filtering procedure applied at the decoder to reduce blockiness. It also utilizes decoding parameters to develop a weighting scheme and adjust the contribution of video frames at the macroblock level to PRNU estimation process. Results obtained on videos captured by 28 cameras show that our approach increases the PRNU matching metric up to more than five times over the conventional estimation method tailored for photos

Oblivious data hiding : a practical approach

This dissertation presents an in-depth study of oblivious data hiding with the emphasis on quantization based schemes. Three main issues are specifically addressed: 1. Theoretical and practical aspects of embedder-detector design. 2. Performance evaluation, and analysis of performance vs. complexity tradeoffs. 3. Some application specific implementations. A communications framework based on channel adaptive encoding and channel independent decoding is proposed and interpreted in terms of oblivious data hiding problem. The duality between the suggested encoding-decoding scheme and practical embedding-detection schemes are examined. With this perspective, a formal treatment of the processing employed in quantization based hiding methods is presented. In accordance with these results, the key aspects of embedder-detector design problem for practical methods are laid out, and various embedding-detection schemes are compared in terms of probability of error, normalized correlation, and hiding rate performance merits assuming AWGN attack scenarios and using mean squared error distortion measure. The performance-complexity tradeoffs available for large and small embedding signal size (availability of high bandwidth and limitation of low bandwidth) cases are examined and some novel insights are offered. A new codeword generation scheme is proposed to enhance the performance of low-bandwidth applications. Embeddingdetection schemes are devised for watermarking application of data hiding, where robustness against the attacks is the main concern rather than the hiding rate or payload. In particular, cropping-resampling and lossy compression types of noninvertible attacks are considered in this dissertation work

Source Camera Verification from Strongly Stabilized Videos

Image stabilization performed during imaging and/or post-processing poses one of the most significant challenges to photo-response non-uniformity based source camera attribution from videos. When performed digitally, stabilization involves cropping, warping, and inpainting of video frames to eliminate unwanted camera motion. Hence, successful attribution requires the inversion of these transformations in a blind manner. To address this challenge, we introduce a source camera verification method for videos that takes into account the spatially variant nature of stabilization transformations and assumes a larger degree of freedom in their search. Our method identifies transformations at a sub-frame level, incorporates a number of constraints to validate their correctness, and offers computational flexibility in the search for the correct transformation. The method also adopts a holistic approach in countering disruptive effects of other video generation steps, such as video coding and downsizing, for more reliable attribution. Tests performed on one public and two custom datasets show that the proposed method is able to verify the source of 23-30% of all videos that underwent stronger stabilization, depending on computation load, without a significant impact on false attribution

Kosova Türklerinin siyasal örgütlenme girişimleri : Kosova Demokratik Türk Partisi

Bu çalışmada “Kosova Türklerinin Siyasi Örgütlenme Girişimleri: Kosova Demokratik Türk Partisi konulu çalışma inşacı kuram çerçevesinde ele alınmıştır. Konunun anlaşılabilirliği açısından Kosova’nın kısa bir tarihi arka planı çizilerek, ülkenin geçtiği üç önemli dönemi; Tito dönemi, Miloşeviç dönemi ve uluslararası toplum vesayeti altında dönemde yaşanan gelişmelere dikkat çekilmiştir. Bunu takiben, tarihsel süreç içerisinde Türk toplumunun varlık mücadelesi, örgütlenme girişimleri, hukuki statüsü ve gelişen olaylara karşı duruşu, söylemi ve mücadeleleri ele alınmıştır. Bu çerçevede, Türk toplumunun varlığını etkileyen önemli gelişmeler nice ki; baskı politikaları, yönetim değişiklikleri, sayımlar, göç olgusu ve devletin azınlık politikaları da irdelenerek, bunların Türk toplumuna etkisi ve Türk toplumunun bunlara refleksleri yansıtılmaya çalışılmıştır. Çalışmada ayrıca, Doğru Yol Derneğinden başlayarak, Türk Demokratik Birliği’nin kuruluşu, Kosova Demokratik Türk Partisine dönüşümü, bölünmesi ve diğer partilerin kurulması konuları üzerinde durulmuştur. Bunun dışında tezin ana aktörü olan, Kosova Demokratik Türk Partisinin ülkenin iç ve dış politikadaki gelişmelere yaklaşımı, söylemi ve eylemleri de örneklerle açıklanarak, çizmeye çalıştığı devletçi politikası örneklerle yansıtılmaya çalışılmıştır. Türk toplumunun ülkede düzenlenen yerel ve genel seçimlere katılımları çerçevesinde seçim platformları, seçim çalışmaları ve seçim sonuçları da karşılaştırılarak, elde edilen başarı ve başarısızlıkların altı çizilmiştir. Seçim sonuçlarından sonra toplumun temsiliyeti ve temsilcilerin yaptıkları çalışmalara da yer verilen çalışmada Türk toplumun geleceği için birlik ver beraberliğin taşıdığı önemin de altı çizilmiştir.This study is heavily based on “Political organization initiatives of Kosovo Turks: Kosovo Democratic Turkish Party” is adrressed within the constructivist theoretical framework. In terms of comprehensibleness of the study, Kosovo`s short historical backgroung is considered in the three important period that is passed by the country: Tito era, Milosevic era and International Community custody emerging developements during the period. Following this, the existential struggle of turkish society, organizational initiatives, their legal status and po sition, attitude towards the facts, statements and struggles are adressed within historical process. In this context, important developements affecting the existence of Turkish society like: repression policies, governing varieties,census, migration fact and state minority policies and it`s effects to the Turkish society and the reflects of Turkish society were examined and tried to be reflected. This study also considers the establishment of Turkish Democratic Union, it`s transformation to Kosovo Democratic Turkish Party, it`s dislocation and establishment of the other parties starting from the Right Path Association. Except this, study will review approaches of the Kosovo Democratic Turkish Party which is main character of the thesis, against States domestic and foreign policy developments, discourses and actions were also explained with examples including the statist policy too. The achievements and failures of the Turkish society are highlighted by comparing election platforms, election practices and election results within the framework of participation level in local and general elections held in the country. Then by the election results, through showing the society representativeness and their mission, study emphasizes the importance of the unity and solidarity for the future of Kosovo Turks

Security issues in watermarking applications - a deeper look

Although it is clear that security is an important issue in digital watermarking applications, the main concerns ad-dressed by the current literature are robustness, capacity and imperceptibility. The inadequacy of the prevailing de-sign paradigm in tackling security issues is mainly due to an incomplete assessment of the threat model. The goal of this paper is to take a detailed and rigorous look at the threat model for a variety of watermarking applications. In this extended abstract, we outline the security requirements for a few common watermarking applications and explore in more detail the threat model for a specific application that involves establishing ownership of multimedia content

Ten years after ImageNet: a 360° perspective on artificial intelligence

It is 10 years since neural networks made their spectacular comeback. Prompted by this anniversary, we take a holistic perspective on artificial intelligence (AI). Supervised learning for cognitive tasks is effectively solved—provided we have enough high-quality labelled data. However, deep neural network models are not easily interpretable, and thus the debate between blackbox and whitebox modelling has come to the fore. The rise of attention networks, self-supervised learning, generative modelling and graph neural networks has widened the application space of AI. Deep learning has also propelled the return of reinforcement learning as a core building block of autonomous decision-making systems. The possible harms made possible by new AI technologies have raised socio-technical issues such as transparency, fairness and accountability. The dominance of AI by Big Tech who control talent, computing resources, and most importantly, data may lead to an extreme AI divide. Despite the recent dramatic and unexpected success in AI-driven conversational agents, progress in much-heralded flagship projects like self-driving vehicles remains elusive. Care must be taken to moderate the rhetoric surrounding the field and align engineering progress with scientific principles

A tool to support the creation of datasets of tampered videos

Digital Video Forensics is getting a growing interest from the Multimedia research community, as the need for methods to validate the authenticity of a video content is increasing with the number of videos freely available to the digital users. Unlike Digital Image Forensics, to our knowledge, there are not standard datasets to test video forgery detection techniques. In this paper we present a new tool to support the users in creating datasets of tampered videos. We furthermore present our own dataset and we discuss some remarks about how to create forgeries difficult to be detected by an observer, to the naked eye