TURIN — Each and every one of the 350 million photos shared every day on Facebook, not to mention those posted on Twitter and Instagram, leaves a "digital footprint," information that sets it apart from the ocean of data constantly being fed into the Internet. Follow the footprint, and one can determine not only where the image came from, but what becomes of it — whether it is being reproduced, for example, without permission.

A team from the Polytechnic University of Turin have come up with an application that does just that. Applying the same technology the European Space Agency (ESA) will use for its upcoming Mars probe, due to be launched in 2018, researchers are able to determine, based on clues contained in each image, the specific device that took the uploaded photo, allowing users to guard against the theft of their digital property.

"This research will have diverse applications, such as the defense of digital copyright on the Internet," says Enrico Magli, coordinator of the "Toothpic" project behind the new app. "We all post photos we didn't take without a second thought."

The app works by identifying the footprints that sensors on electronic devices — from cameras to smartphones — leave on each photograph. Until recently it was impossible to compress this data and compare it in a large-scale database. But the Polytechnic team came up with a way to sidestep the problem. "We developed a technology that reduces the size of this photographic DNA by a thousand times, allowing us to research on large databases such as social networks," Magli explains.

Originally, the team didn't expect to apply their technology to photographic cameras. The concept ocurred to them almost accidentally, while attending a tech conference. From there the Toothpic project obtained 150,000 euros from the European Union to finance development of the app. In the meantime, the team applied to register two patents, one for the data compression technology and another for the large-scale use of photographic footprints. They expect to complete their project within the next three months before establishing a startup to sell the new inventions.

The Toothpic technology can do more than help people safeguard their digital copyright. At one point the team was contacted to help a photographer who had lost his camera. Another potential use is helping the police sift through millions of images to determine if an illegal pornographer, for example, has authored other illicit photographs.

The research could also abolish the use of passwords: A user could identify themselves simply by uploading a photo with their unique digital footprint. Or it could lead to new digital friendships around the world. Imagine liking a photo on Facebook and seeing a message appear putting you in contact with the author of the image — whomever they may be, and wherever they may live.