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CAPTCHA is now almost a standard security technology, and has found widespread application in commercial websites. Usability and robustness are two fundamental issues with CAPTCHA, and they often interconnect with each other. This paper discusses usability issues that should be considered and addressed in the design of CAPTCHAs. Some of these issues are(More)
CAPTCHA is now almost a standard security technology. The most widely deployed CAPTCHAs are text-based schemes, which typically require users to solve a text recognition task. The state of the art of CAPTCHA design suggests that such text-based schemes should rely on segmentation resistance to provide security guarantee, as individual character recognition(More)
Visual CAPTCHAs have been widely used across the Internet to defend against undesirable or malicious bot programs. In this paper, we document how we have broken most such visual schemes provided at Captchaservice.org, a publicly available web service for CAPTCHA generation. These schemes were effectively resistant to attacks conducted using a high-quality(More)
BACKGROUND Projections of cancer incidence are important for planning health services and to provide a baseline for assessing the impact of public health interventions. METHODS Rates estimated from smooth function age-period-cohort modelling of cancer incidence data from Great Britain 1975 to 2007 are extrapolated to 2030 and applied to UK population(More)
Sir, We would like to thank Oliver et al (2013) for bringing to our attention these data issues. After careful checking, it is clear that the main source of discrepancy is the difference between the numbers of cancer registrations for 2004–2007, as available in 2010, and the updated numbers released in 2011. Whereas we were aware that there can be(More)
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