![]() ![]() In 2010, Pete Ringwood created the “” website as a free service where people could submit photos and web pictures for analysis. Error Level Analysis (ELA) is one of the simpler methods presented by the researcher. Neal Krawetz made an interesting presentation during the Black Hat conference titled “A Picture’s Worth.” It involved determing if a picture is real, or of a computer modification. In a modified image, the altered grid should be at a higher error potential in respect to remaining part of the image. Each square should degrade at approximately the same rate, due to the introduction of an homogeneous amount of errors across the entire image. They result in poor quality compressed images.įor images not digitally modified, all 8×8 grids should have a similar error level, resaving the picture. ![]() The 8X8 dimension was chosen after numerous experiments with other sizes, any matrices of sizes greater than 8 X 8 are harder to be mathematically manipulated or not supported by hardware, meanwhile any matrices of sizes less than 8 X 8 don’t have enough information. The JPEG algorithm works on image grids, compressed independently, having a size of 8×8 pixels. A JPEG compression scale is usually 10:1. The level of compression could be chosen as a reasonable compromise between picture size and image quality. It’s a data encoding algorithm that compresses data by discarding (losing) some of it. JPEG (Joint Photographic Experts Group) is a method of lossy compression for digital images. To better understand the techniques, it’s necessary to deepen the JPEG compression technique. The technique could be used to determine if a picture has been digitally modified. ![]() By: Pierluigi Paganini from Infosec InstituteĮrror Level Analysis is a forensic method to identify portions of an image with a different level of compression. ![]()
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