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    TAPCHA - An 'Invisible' CAPTCHA Scheme

    HCI 2018

    Proceedings of the 32nd International BCS Human Computer Interaction Conference (HCI 2018)

    Belfast, UK, 4 - 6 July 2018


    Nan Jiang & Huseyin Dogan



    TAPCHA is a universal CAPTCHA scheme designed for touch-enabled smart devices such as smartphones, tablets and smartwatches. The main difference between TAPCHA and other CAPTCHA schemes is that TAPCHA retains its security by making the CAPTCHA test ‘invisible’ for the bot. It then utilises context effects to maintain the readability of the instruction for human users which eventually guarantees the usability of the scheme. Two reference designs, namely TAPCHA SHAPE & SHADE and TAPCHA MULTI are developed to demonstrate the use of this scheme.


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