A digital signature in online photos can help trace child pornography to child abusers.
A new photo forensic technique may help track down and catch peddlers of child pornography.
The new technique was identified by Riccardo Satta, scientific project officer of the European Commission Joint Research Centre’s Institute for the Protection and Security of the Citizen. It focuses on a photo “signature,” a unique set of patterns permanently imprinted onto an image during the capturing process.
These signatures are created through a camera’s digital light sensor, which adds “noise” or interference to every image.
“It is not currently possible to perfectly separate the image from the noise, modify the noise and then add it back to the image,” Satta told the Scientific American. “Trying to fake it by substituting it [noise] with another one will probably create a lot of visible artifacts [whereas] removing it will likely result in a blurry and unnatural image.”
In a study of 2,896 images taken from 15 different social networks and blogs, Satta was able to match a photo with its owner 50 percent of the time using software he had developed. He was also able to pair the photo with its camera 90 percent of the time.
“Those rates would not be high enough to use in court as evidence against someone suspected of a crime,” Scientific American added. “But they could help select targets for investigation, especially with accuracy enhanced by other information commonly found on social networks, such as location, friends lists, and other contextual data.”
Since launching in 1998, the CyberTipline received more than 1.9 million reports of suspected child pornography online. The National Center for Missing and Exploited Children’s Child Victim Identification Program has reviewed more than 90 million child pornography images since it was started in 2002, the Sun Chronicle reported.
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