Camera Model Identification with Convolutional Neural Networks and Image Noise Pattern

Camera source detection has drawn a lot of attention in past decade. It enables us to solve a wide range of problems, from crime evidence identification to photo tampering detection. In this paper, some main methods people used in this area for past decade will be reviewed in the Introduction and Method sections. Also in the Method and Result sections, I compared and improved state-of-the-art approaches to solve camera model identification problem. In the latter part, I proposed a novel approaches based on Convolutional Neural Networks and Image Noise Pattern. Results on the dataset from Kaggle shows that to identify source camera, Convolutional Neural Networks can be applied to the pattern noise rather than directly to the original pictures to achieve at least similar or even better performance.Ope

PRNU Estimation based on Weighted Averaging for Source Smartphone Video Identification

Photo response non-uniformity (PRNU) noise is a sensor pattern noise characterizing imperfections in the imaging device. The PRNU is a unique noise for each sensor device, and it has been generally utilized in the literature for source camera identification and image authentication. In video forensics, the traditional approach estimates the PRNU by averaging a set of residual signals obtained from multiple video frames. However, due to lossy compression and other non-unique content-dependent noise components that interfere with the video data, constant averaging does not take into account the intensity of these undesirable noise components which are content-dependent. Different from the traditional approach, we propose a video PRNU estimation method based on weighted averaging. The noise residual is first extracted for each single video. Then, the estimated noise residuals are fed into a weighted averaging method to optimize PRNU estimation. Experimental results on two video datasets captured by various smartphone devices have shown a significant gain obtained with the proposed approach over the conventional state-of-the-art one

Three Dimensional Denoising Filter For Effective Source Smartphone Video Identification and Verification

The field of digital image and video forensics has recently seen significant advances and has attracted attention from a growing number of researchers given the availability of imaging functionalities in most current multimedia devices at no cost including smartphones and tablets. Photo response non-uniformity (PRNU) noise is a sensor pattern noise characterizing the imaging device. However, estimating the PRNU from smartphone videos can be a challenging process because of the lossy compression that digital videos normally undergo for various reasons in addition to other non-unique noise components that interfere with the video data. This paper presents a new filtering technique for PRNU estimation based on the three-dimensional discrete wavelet transform followed by a 3D wiener filter. The rationale is that the 3D filter can filter out the compression artifacts along the temporal dimension in a more effective way than simple averaging. Experimental results on a public video dataset captured by various smartphone devices have shown a significant gain obtained with the proposed approach over the well-known two-dimensional wavelet-based Wiener approach

On the Sensor Pattern Noise Estimation in Image Forensics: A Systematic Empirical Evaluation

Extracting a fingerprint of a digital camera has fertile applications in image forensics, such as source camera identification and image authentication. In the last decade, Photo Response Non_Uniformity (PRNU) has been well established as a reliable unique fingerprint of digital imaging devices. The PRNU noise appears in every image as a very weak signal, and its reliable estimation is crucial for the success rate of the forensic application. In this paper, we present a novel methodical evaluation of 21 state-of-the-art PRNU estimation/enhancement techniques that have been proposed in the literature in various frameworks. The techniques are classified and systematically compared based on their role/stage in the PRNU estimation procedure, manifesting their intrinsic impacts. The performance of each technique is extensively demonstrated over a large-scale experiment to conclude this case-sensitive study. The experiments have been conducted on our created database and a public image database, the 'Dresden image databas

Weighted averaging-based sensor pattern noise estimation for source camera identification

Sensor pattern noise has been broadly used in the literature for image authentication and source camera identification. The abundant information that a sensor pattern noise carries in terms of the frequency content makes it unique and hence suitable for source camera identification. The traditional approach for estimating the sensor pattern noise uses a set of images to estimate a pattern residual signal from each image. The estimated residual signals are then averaged to obtain the sensor pattern noise. This is based on the assumption that each residual signal is a noisy observation of the sensor pattern noise. Such an assumption is well justified in practice because the images are acquired under different conditions making the corresponding residual signals distinct from each other. For instance bright images provide better sensor pattern noise estimation than dark images. Also, saturated pixels cause undesirable noise in residual signals. Inspired by this observation, a weighted averaging approach is proposed for efficient sensor pattern noise estimation. The proposed approach has been validated with two sensor pattern noise estimation techniques from the literature and significant improvements have been shown through experimental results

Temporal Image Forensics for Picture Dating based on Machine Learning

Temporal image forensics involves the investigation of multi-media digital forensic material related to crime with the goal of obtaining accurate evidence concerning activity and timing to be presented in a court of law. Because of the ever-increasing complexity of crime in the digital age, forensic investigations are increasingly dependent on timing information. The simplest way to extract such forensic information would be the use of the EXIF header of picture files as it contains most of the information. However, these header data can be easily removed or manipulated and hence cannot be evidential, and so estimating the acquisition time of digital photographs has become more challenging. This PhD research proposes to use image contents instead of file headers to solve this problem. In this thesis, a number of contributions are presented in the area of temporal image forensics to predict picture dating. Firstly, the present research introduces the unique Northumbria Temporal Image Forensics (NTIF) database of pictures for the purpose of temporal image forensic purposes. As digital sensors age, the changes in Photo Response Non-Uniformity (PRNU) over time have been highlighted using the NTIF database, and it is concluded that PRNU cannot be useful feature for picture dating application. Apart from the PRNU, defective pixels also constitute another sensor imperfection of forensic relevance. Secondly, this thesis highlights the fact that the filter-based PRNU technique is useful for source camera identification application as compared to deep convolutional neural networks when limited amounts of images under investigation are available to the forensic analyst. The results concluded that due to sensor pattern noise feature which is location-sensitive, the performance of CNN-based approach declines because sensor pattern noise image blocks are fed at different locations into CNN for the same category. Thirdly, the deep learning technique is applied for picture dating, which has shown promising results with performance levels up to 80% to 88% depending on the digital camera used. The key findings indicate that a deep learning approach can successfully learn the temporal changes in image contents, rather than the sensor pattern noise. Finally, this thesis proposes a technique to estimate the acquisition time slots of digital pictures using a set of candidate defective pixel locations in non-overlapping image blocks. The temporal behaviour of camera sensor defects in digital pictures are analyzed using a machine learning technique in which potential candidate defective pixels are determined according to the related pixel neighbourhood and two proposed features called local variation features. The idea of virtual timescales using halves of real time slots and a combination of prediction scores for image blocks has been proposed to enhance performance. When assessed using the NTIF image dataset, the proposed system has been shown to achieve very promising results with an estimated accuracy of the acquisition times of digital pictures between 88% and 93%, exhibiting clear superiority over relevant state-of-the-art systems