Ahmet Emir Dirik

Ahmet Emir Dirik
Uludag University · Department of Computer Engineering

Professor

About

44
Publications
6,870
Reads
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880
Citations
Additional affiliations
May 2012 - November 2015
Uludag University
Position
  • Professor (Assistant)
January 2005 - May 2010
Polytechnic Institute of New York University
Position
  • Research Assistant

Publications

Publications (44)
Conference Paper
We develop a model to identify the most likely regions for users to click in order to create graphical passwords in the PassPoints system. A PassPoints password is a sequence of points, chosen by a user in an image that is displayed on the screen. Our model predicts probabilities of likely click points; this enables us to predict the entropy of a c...
Article
Digital single lens reflex cameras suffer from a well-known sensor dust problem due to interchangeable lenses that they deploy. The dust particles that settle in front of the imaging sensor create a persistent pattern in all captured images. In this paper, we propose a novel source camera identification method based on detection and matching of the...
Article
The availability of sophisticated source attribution techniques raises new concerns about privacy and anonymity of photographers, activists, and human right defenders who need to stay anonymous while spreading their images and videos. Recently, the use of seam-carving, a content-aware resizing method, has been proposed to anonymize the source camer...
Article
Analogous to use of bullet scratches in forensic science, the authenticity of a digital image can be verified through the noise characteristics of an imaging sensor. In particular, photo-response non-uniformity noise (PRNU) has been used in source camera identification (SCI). However, this technique can be used maliciously to track or inculpate inn...
Conference Paper
In this paper, we introduce tamper detection techniques based on artifacts created by color filter array (CFA) processing in most digital cameras. The techniques are based on computing a single feature and a simple threshold based classifier. The efficacy of the approach was tested over thousands of authentic, tampered, and computer generated image...
Article
Gearbox bearings are critical elements of wind power generation systems. Their stable operation supports the power generation, thus reducing the downtime and improving the economic efficiency of wind farms. With the wide availability of sensors, data-driven methods have started to be utilized instead of physical-based methods for condition monitori...
Conference Paper
Gears are critical power transmission elements used in various industries. However, varying working speeds and sudden load changes may cause root cracks, pitting, or missing tooth failures. The asymmetric tooth profile offers higher load-carrying capacity, long life, and the ability to lessen vibration than the standard (symmetric) profile spur gea...
Conference Paper
Gear mechanisms are one of the most significant components of the power transmission systems. Due to increasing emphasis on the high-speed, longer working life, high torques, etc. cracks may be observed on the gear surface. Recently, Machine Learning (ML) algorithms have started to be used frequently in fault diagnosis with developing technology. T...
Preprint
Full-text available
PRNU based camera recognition method is widely studied in the image forensic literature. In recent years, CNN based camera model recognition methods have been developed. These two methods also provide solutions to tamper localization problem. In this paper, we propose their combination via a Neural Network to achieve better small-scale tamper detec...
Article
Patch-Match is an efficient algorithm used for structural image editing and available as a tool on popular commercial photo-editing software. The tool allows users to insert or remove objects from photos using information from similar scene content. Recently, a modified version of this algorithm was proposed as a counter-measure against Photo-Respo...
Article
Full-text available
Photo Response Non-Uniformity (PRNU) is a camera imaging sensor imperfection which has earned a great interest for source device attribution of digital videos. The majority of recent researches about PRNU-based source device attribution for digital videos do not take into consideration the effects of video compression on the PRNU noise in video fra...
Article
Full-text available
ENF is a time-varying signal of the frequency of mains electricity in a power grid. It continuously fluctuates around a nominal value (50/60 Hz) due to changes in supply and demand of power over time. Depending on these ENF variations, the luminous intensity of a mains-powered light source also fluctuates. These fluctuations in luminance can be cap...
Chapter
Full-text available
This paper studies the problem of vehicle make & model classification. Some of the main challenges are reaching high classification accuracy and reducing the annotation time of the images. To address these problems, we have created a fine-grained database using online vehicle marketplaces of Turkey. A pipeline is proposed to combine an SSD (Single...
Article
Full-text available
This paper comprises an evaluation of electromagnetic shielding effectiveness of woven fabrics containing stainless steel wire with a new mobile based method. Cross covered hybrid weft yarns were produced with polyester and stainless steel metal wires. The conductive fabrics were produced by using the hybrid weft and texturized polyester warp yarns...
Article
Full-text available
ENF (Electrical Network Frequency) instantaneously fluctuates around its nominal value (50/60 Hz) due to a continuous disparity between generated power and consumed power. Consequently, luminous intensity of a mains-powered light source varies depending on ENF fluctuations in the grid network. Variations in the luminance over time can be captured f...
Article
Full-text available
Video dosyalarının Elektrik Şebeke Frekansı (Electric Network Frequency - ENF) temelli adli kanıt analizi tekniği, çoklu ortam dosyalarının kayıt zamanını doğrulamada ve dosyalarda yapılan sahteciliği tespit etmede son yıllarda önerilmiş en önemli araçlardan biridir. ENF, şebekede üretilen toplam gücün tüketilen toplam güce göre artıp azalmasına ba...
Article
In this study, we introduce an alternative method to evaluate the electromagnetic shielding effectiveness (EMSE) of woven fabrics containing metal wires. For experimental measurements, hybrid silk viscose yarns containing metal wires were first produced. Conductive test fabrics were then produced using the hybrid weft yarns and polyester warp yarns...
Conference Paper
Photo response noise uniformity (PRNU) based source attribution has proven to be a powerful technique in multimedia forensics. The increasing prominence of this technique, combined with its introduction as evidence in the court, brought with it the need for it to withstand anti-forensics. Although robustness under common signal processing operation...
Patent
Full-text available
This invention is about anonymization of digital images (I), through elimination of the Photo-Response Non Uniformity (N) noise pattern which is unique to the imaging sensor and latent in all digital images taken by digital cameras or devices with imaging sensors (1).
Patent
Full-text available
An image encryption method that includes receiving image data based on an image, wherein the image data comprises a plurality of pixel values, and permuting a plurality of, and preferably all of, the pixel values using at least a secret key to create permuted image data. Also, an image decryption method that includes scanning a printed image to cre...
Conference Paper
Full-text available
Current image encryption schemes do not achieve robustness to lossy compression and downsizing without sacrificing image quality. In this paper, we introduce a selective robust image encryption scheme for online social networks that provides a trade-off between robustness and security. With the selective encryption property, users have an option to...
Article
A copy detection pattern (CDP) is a shape (typically a rectangle) filled with pixels of random grey levels and incorporated in a digital document to be printed as a unique physical document. It is a powerful tool to detect copies. Whenever a document is printed and scanned, the grey levels of the pixels intermix in a measurable way. When a document...
Chapter
Recent studies in multimedia forensics show that digital images contain intrinsic patterns, traces, and marks generated by imaging pipeline components (sensor) and processes (demosaicing and color adjustment). Some of these patterns and marks, such as photo response non-uniformity noise (PRNU), are unique to individual component characteristics of...
Conference Paper
In this Note we summarize our research on increasing the information scent of video recordings that are shared via email in a corporate setting. We compare two types of email messages for sharing recordings: the first containing basic information (e.g. title, speaker, abstract) with a link to the video; the second with the same information plus a s...
Conference Paper
The identification of image acquisition source is an important problem in digital image forensics. In this work, we focus on building a classifier to effectively distinguish between digital images taken from digital single lens reflex (DSLR) and compact cameras. Based on the architecture and the imaging features of DSLR and compact cameras, the ima...
Conference Paper
In this paper, a novel individual source scanner identification scheme is proposed. The scheme uses traces of dust, dirt, and scratches over scanner platen on scanned images to characterize a source scanner. The efficacy of the proposed scheme is substantiated with experimental analysis. The robustness of the scheme to the JPEG compression is also...
Conference Paper
A problem associated with digital single lens (DSLR) cameras is sensor dust. This problem arises due to dust particles attracted to the sensor, when the interchangeable lens is removed, creating a dust pattern in front of the imaging sensor. Sensor dust patterns reveals themselves as artifacts on the captured images and they become more visible at...
Conference Paper
Discrimination of computer generated images from real images is becoming more and more important. In this paper, we propose the use of new features to distinguish computer generated images from real images. The proposed features are based on the differences in the acquisition process of images. More specifically, traces of demosaicking and chromati...
Conference Paper
Recently proposed perturbed quantization (PQ) data hiding is a novel steganographic scheme which is undetectable with the current steganalysis methods. In this paper PQ steganography scheme is described briefly and a novel singular value decomposition (SVD) based Steganalysis method is proposed to detect PQ embedding. The proposed SVD based stegana...
Article
As land-vehicles almost always moves on roads, most of vehicle tracking systems, projects the vehicle positions on digital road segments. Vehicle tracking systems generally use dead reckoning and global positioning system (GPS) in order to get geographical vehicle position information. These positioning technologies have limitations either in accur...

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