Microsoft announced on Dec. 15 that it would donate PhotoDNA, a technology developed by Microsoft Research, to the National Center for Missing & Exploited Children, which will use it to identify and eliminate images of child sexual abuse and exploitation.

PhotoDNA works by analyzing the properties of an image and using that to create a unique signature, also known as a hash. PhotoDNA then compares the digital image's signature with another image to determine if the two are a match, even if the latter image has been somehow altered by being saved in a different format, resized or digitally edited. Hany Farid, an expert in digital forensics technology at Dartmouth, apparently developed some of the computational tools used by Microsoft and NCMEC to refine PhotoDNA.

"Everybody's aware that you can manipulate images, sounds and video. What we've been trying to do is bring some trust back to that underlying media," Farid said in a Dec. 15 post on a Microsoft site about the project. "The tiniest change to the image and the signature would be completely different ... the PhotoDNA technology extends the signature to make it robust and reliable, so even if you change the image a little bit, we can still find it."

PhotoDNA is also automated, allowing NCMEC to scan through millions of images online in order to quickly find matches. Farid suggests that the technology can process even a billion images in a relatively rapid fashion. Once NCMEC begins assigning PhotoDNA signatures to explicit images, then online service providers can use those signatures to ferret out any other copies of those images on their networks. According to Microsoft, NCMEC has reviewed and analyzed almost 30 million such images, along with video, since 2003.

Microsoft's Website about its joint effort with the NCMEC to battle online child abuse can be found here.

Technology for a good cause, no?