Tracking a photo's digital DNA

By Peter Griffin 20/03/2012

The Government is set to introduce technology aimed at combatting the trade in child sex abuse images by identifying images and therefore their spread via the internet through their digital DNA.

The Department of Internal Affairs’ Censorship Compliance Unit will deploy Microsoft’s PhotoDNA technology.  Micrsoft has a digital crimes unit and in recent years has ramped up its efforts in developing software to fight electronic crime. This is a great move as it will help investigators track the spread and hopefully identify the source of child sex images – and help catch the people who peddle such filth.

How does PhotoDNA work? According to Microsoft:

PhotoDNA uses a mathematical technique known as robust hashing that works by calculating a unique signature into a ’hash’ that represents the essence of a particular photo. In the same way that the characteristics of every person’s DNA are different, the signature or ’hash value’ for every photo is different, enabling the creation of a hash that can identify an image based on its unique characteristics or its ’digital DNA.’ Although a photo’s hash cannot be used to re-create an image or identify people or items within an image, it can be compared with hashes of other photos as a reliable way to match two different copies of the same image.

This diagram explains how it works…


0 Responses to “Tracking a photo's digital DNA”

  • So it’s immune to someone who say, adjusts the ‘levels’ or ‘exposure’ on the picture and/or adjusts the sharpness?

  • As I understand it the gradient information is still able to be detected after changes like the levels being altered or the sharpness being adjusted. So if someone tries to blur out someone’s face in a photo it can still be linked back to the original photo or an earlier version, allowing investigators to piece together where it came from.