In a system and method for the generation of attack-resistant, user-friendly, image-based CAPTCHAs (Completely Automated Public test to Tell Computers and Humans Apart), controlled distortions are applied to randomly chosen images and presented to a user for annotation from a given list of words. An...http://www.google.fr/patents/US7929805?utm_source=gb-gplus-shareBrevet US7929805 - Image-based CAPTCHA generation system
