Ideas on authenticating humanness in collaborative systems using AI-hard problems in perception and cognition

Collaborative applications including email, chat, file-sharing networks, blogs, and gaming are under constant threat of automated programs that are gaining access to, attacking, degrading, or otherwise disrupting the intended communications and interactions. Thus, an important issue in collaborative systems security is how to verify that a user is a human, and not a computer attempting to access the system for malicious purposes. We propose and discuss several AI-hard examples from perception and cognition that may be useful for distinguishing between human-level intelligence and artificial intelligence.