Microsoft is donating a new technology to the National Center for Missing & Exploited Children (NCMEC) that has the potential to make a drastic difference in the fight against the spread of child pornography online. The technology, called PhotoDNA, was initially created by Microsoft Research. It was further developed by Hany Farid…to help NCMEC in its efforts to find hidden copies of the worst images of child sexual exploitation known today…The basis for PhotoDNA is a technology called “robust hashing,” which calculates the particular characteristics of a given digital image — its digital fingerprint or “hash value” — to match it to other copies of that same image…Once NCMEC assigns PhotoDNA signatures to known images of abuse, those signatures can be shared with online service providers, who can match them against the hashes of photos on their own services, find copies of the same photos and remove them. Also, by identifying previously “invisible” copies of identified photos, law enforcement may get new leads to help track down the perpetrators.