Sentence First CAPTCHA: Proposal and study of a text based CAPTCHA scheme
Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
A major problem on the Internet is automated computer programs abusing services intendedto be used only by humans. Therefore, a method is needed to separate computersfrom humans. Completely Automated Public Turing Test To Tell Computers and HumansApart, or CAPTCHA, is a term used to describe a test that is difficult for computers andeasy for humans to pass and that can be generated and graded automatically. Most of theCAPTCHA schemes currently in use rely on some kind of image or audio recognitionproblem, making them unavailible to the visually and/or audially impaired. Additionally,visual CAPTCHAs can currently be broken with alarmingly high success rates. We proposea CAPTCHA scheme based purely in the text domain which we have named SentenceFirst CAPTCHA. The problem imposed on the users consists of classifying stochasticallygenerated sentences by fluency and legibility and pairs of sentences by semantic coherence.This scheme was implemented and tested by means of several surveys. The answers wereanalysed and the results show that this could very well be a feasible CAPTCHA scheme.
Place, publisher, year, edition, pages
2011. , 24 p.
IdentifiersURN: urn:nbn:se:hig:diva-9392OAI: oai:DiVA.org:hig-9392DiVA: diva2:422117
Subject / course