Making complex data simple and compelling
From digital device to digital evidence
Unlock your vehicle's digital evidence potential
Forensic Analysis and Enhancement
Investigating and analyzing financial records
Gain access to the online accounts of deceased loved ones
Clear, precise evidence for a messy world
Expert reports to suit your specific needs
We can locate people anywhere
Stop worrying and learn the truth
Prevent, Detect, Respond To Cyberattacks
First response is crucial. Every minute counts.
The first response is critical to reduce liability
Detection & Removing Spyware Services
Reduce your electronic risk from digital transmittals
Find out who you are really talking to
Experienced, Confidential Services
Swift, professional incident response
Complicated cases require compelling digital facts
Find, recover and document digital evidence
Bring solid evidence before a judge
Cases can be investigated using Social Media
Divorce, custody battles, and other
Win the most important battle of your life
Everything you need
Effective Expert Witness in Court
Evidence shows who is telling the truth
Subpoena power yields strong evidence
Digital evidence can build a strong defense
Nowadays Error Level Analysis or ELA has become the most common method for image modification detection. This method is used by lots of both commercial and free tools and web-services [1, 2].
This method is based on the fact that JPEG image compression removes overmuch information about original’s brightness and color . The amount of information being removed depends on compression rate and, of course, signal quantization matrix. If original image compressed only once is quantizated by the same matrix as the original, modified image won’t be different from the original. But if the original image is saved in JPEG a number of times, there will be significant differences between the original and modified image . The result of ELA is error pattern, which shows differences between the original and modified image. The aim of the forensic examiner is to interpret error pattern right.
This method works very well for modification detection in images created from fragments with different error level (fig. 1, 2).
Figures 1,2. Modified image and its error pattern
But if fragments are taken from files with the same error level or are cloned from the same image, such analysis won’t bring good results, especially when your tool doesn’t allow to choose compression rate value for calculating error pattern (fig. 3, 4, 5).
Figure 3. An image compressed with 85 quality created from fragments of an image with 50 quality
Figure 4. Error pattern calculated for 85 quality
Figure 5. Error pattern calculated for 50 quality. Now we can see cloned fragments
The chances of successful modification detection depend on technique of editing used. For example, if fragment was pasted in a cropped image which wasn’t saved in between, reliability of the method decreases. The same can be said about highly compressed images.
As you already know, you can use ELA not only to detect fragments pasting, but also some other image modifications, read about it here.
Interests: Digital Video Forensics, Forgery Detection, Audio Forensics
Interests: Computer, Cell Phone & Chip-Off Forensics
Interests: iOS forensics, Android forensics, Mac OS X forensics, Windows forensics, Linux forensics
Save my name, email, and website in this browser for the next time I comment.
Speak to a Specialist Now