  We demonstrate that modern image recognition methods based on artificial
neural networks can recover hidden information from images protected by various
forms of obfuscation. The obfuscation techniques considered in this paper are
mosaicing (also known as pixelation), blurring (as used by YouTube), and P3, a
recently proposed system for privacy-preserving photo sharing that encrypts the
significant JPEG coefficients to make images unrecognizable by humans. We
empirically show how to train artificial neural networks to successfully
identify faces and recognize objects and handwritten digits even if the images
are protected using any of the above obfuscation techniques.
