Leveraging human computation for pure-text Human Interaction Proofs

•Pure-text HIPs provide desirable usability and accessibility, but not security.•We propose using human computation to generate them and reproduce automatically.•Our system, SMARTCHA, proactively checks the security of human-generated HIPs.•22 000 questions were generated, a usability study was held with 372 participants.•Usability study shows that solving SMARTCHA HIPs is significantly more enjoyable.

Even though purely text-based Human Interaction Proofs (HIPs) have desirable usability and accessibility attributes; they could not overcome the security problems yet. Given the fact that fully automated techniques to generate pure-text HIPs securely do not exist, we propose leveraging human computation for this purpose. We design and implement a system called SMARTCHA, which involves a security engine to perform automated proactive checks on the security of human-generated HIPs and a module for combining human computation with automation to increase the number of HIP questions. In our work, we employ HIP operators who generate around 22 000 questions in total for SMARTCHA system. With a user study of 372 participants, we evaluate the usability of SMARTCHA system and observe that users find solving pure-text HIPs of SMARTCHA system significantly more enjoyable than solving reCAPTCHA visual HIPs.