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CAPTCHA

This CAPTCHA (reCAPTCHA v1) of "smwm" obscures its message from computer interpretation by twisting the letters and adding a slight background color gradient.

A CAPTCHA (/ˈkæp.tʃə/ KAP-chə) is a type of challenge–response test used in computing to determine whether the user is human in order to deter bot attacks and spam.[1]

The term was coined in 2003 by Luis von Ahn, Manuel Blum, Nicholas J. Hopper, and John Langford.[2] It is a contrived acronym for "Completely Automated Public Turing test to tell Computers and Humans Apart."[3] A historically common type of CAPTCHA (displayed as reCAPTCHA v1) was first invented in 1997 by two groups working in parallel. This form of CAPTCHA requires entering a sequence of letters or numbers in a distorted image. Because the test is administered by a computer, in contrast to the standard Turing test that is administered by a human, CAPTCHAs are sometimes described as reverse Turing tests.[4]

Two widely used CAPTCHA services are Google's reCAPTCHA[5][6] and the independent hCaptcha.[7][8] It takes the average person approximately 10 seconds to solve a typical CAPTCHA.[9]

  1. ^ "The reCAPTCHA Project – Carnegie Mellon University CyLab". www.cylab.cmu.edu. Archived from the original on 27 October 2017. Retrieved 13 January 2017.
  2. ^ Cite error: The named reference abhl was invoked but never defined (see the help page).
  3. ^ "What is CAPTCHA?". Google Support. Google Inc. Archived from the original on 6 August 2020. Retrieved 9 September 2022. CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a [...]
  4. ^ Mayumi Takaya; Yusuke Tsuruta; Akihiro Yamamura (30 September 2013). "Reverse Turing Test using Touchscreens and CAPTCHA" (PDF). Journal of Wireless Mobile Networks, Ubiquitous Computing, and Dependable Applications. 4 (3): 41–57. doi:10.22667/JOWUA.2013.09.31.041. Archived (PDF) from the original on 22 August 2017.
  5. ^ "What is reCAPTCHA? –?reCAPTCHA Help". support.google.com. Archived from the original on 20 July 2023. Retrieved 20 July 2023.
  6. ^ Sulgrove, Jonathan (7 July 2022). "reCAPTCHA: What It Is and Why You Should Use It on Your Website – TSTS". Twin State Technical Services. Archived from the original on 10 November 2022. Retrieved 10 November 2022.
  7. ^ "Websites using hCaptcha". trends.builtwith.com. Archived from the original on 10 November 2022. Retrieved 10 November 2022.
  8. ^ "hCaptcha – About Us". www.hcaptcha.com. Archived from the original on 20 July 2023. Retrieved 20 July 2023.
  9. ^ Bursztein, Elie; Bethard, Steven; Fabry, Celine; Mitchell, John C.; Jurafsky, Dan (2010). "How Good Are Humans at Solving CAPTCHAs? A Large Scale Evaluation" (PDF). 2010 IEEE Symposium on Security and Privacy. pp. 399–413. CiteSeerX 10.1.1.164.7848. doi:10.1109/SP.2010.31. ISBN 978-1-4244-6894-2. S2CID 14204454. Archived (PDF) from the original on 8 August 2018. Retrieved 30 March 2018.

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