This presentation provides an introduction to the digital image forgery topic.

1. Digital Image
Forgery
Mohamed Talaat
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2. Agenda
• What is Digital Image Forgery?
• Types of Digital Image Forgery
– Image Retouching
– Image Splicing
– Image Cloning
• Forgery Detection Mechanisms
– Active Methods
– Passive Methods
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3. 3
What is Digital Image Forgery?
• The process of creating fake image has been
tremendously simple with the introduction of powerful
computer graphics editing software such as Adobe
Photoshop, GIMP, and Corel Paint Shop, some of which
are available for free.
• Alteration of the semantic components of a digital
image:
– Removing Contents from the image
– Adding Data to the image

4. 4
Types of Digital Image Forgery
• There are many cases of digital image forgery.
• All of these cases can be categorized into three major
groups, based on the process involved in creating the
fake image:
– Image Retouching
– Image Splicing (Copy-Paste)
– Image Cloning (Copy-Move)

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Image Retouching?
• It is one of the oldest types of image forgery:
– Image features are tampered with.
– Used to enhance or reduce digital image features.
– Considered less dangerous type of image forgery.

6. 6
Image Splicing (Copy-Paste)
• Fragments of 2 or more images are combined to form an image.
• This operation is fundamental in digital photo montaging and in turn
is a mechanism for image forgery creation.
• Image splicing technique may change the visual message of digital
images more aggressively than image retouching.

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Image Cloning (Copy-Move)
• Considered as a special case of image splicing, where the tampering
occurs within a single image and no need for multiple images.
• Part of the image is copied and then pasted in a desired location
within the same image.
• The purpose of such tampering is to duplicate or conceal a certain
object in that image.

8. 8
Image Cloning (Copy-Move)
• Blurring is usually used to reduce the expected irregularity along the
border of the pasted regions.
• The similarity of texture, color, noise and other information inside the
image make it very difficult to detect this kind of tampering via visual
inspection.
• Moreover, performing of post-processing operations such as blurring,
adding noise and JPEG compression or geometric operations such as
scaling, shifting and rotation increase the hardness of detection
task.

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Forgery Detection Mechanisms
• Forgery detection mechanisms can be classified into
two types:
– Active Methods
– Passive Methods
• Active Methods
– Hidden Information inside the Digital Image.
– Done at the time of Data Acquisition or before disseminated to
the public.
– Embedded information can be used to identify the source of
such image or to detect possible modification to that image.

10. 10
Forgery Detection Mechanisms
(Active Methods)
• Two major types:
– Digital Signature
– Digital Watermarking

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Forgery Detection Mechanisms
(Passive Methods)
• Use traces left by the processing steps in different phases of
acquisition and storage of digital images.
• These traces can be treated as a fingerprint of the image source
device.
• Passive methods work in the absence of protecting techniques.
• They do not use any pre-image distribution information inserted
into digital image.
• They work by analyzing the binary information of digital image in
order to detect forgery traces, if any
• Limitation is the number of false positives.

12. Thanks 
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