Study of Hollow Letter CAPTCHAs Recognition Technology Based on Color Filling Algorithm


Huishuang Shao, Yurong Xia, Kai Meng, and Changhao Piao, Journal of Information Processing Systems Vol. 19, No. 4, pp. 540-553, Aug. 2023  

https://doi.org/10.3745/JIPS.02.0202
Keywords: Color Filling, Contour Restoration, De-noising, Hollow CAPTCHA
Fulltext:

Abstract

The hollow letter CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is an optimized version of solid CAPTCHA, specifically designed to weaken characteristic information and increase the difficulty of machine recognition. Although convolutional neural networks can solve CAPTCHA in a single step, a good attack result heavily relies on sufficient training data. To address this challenge, we propose a seed filling algorithm that converts hollow characters to solid ones after contour line restoration and applies three rounds of detection to remove noise background by eliminating noise blocks. Subsequently, we utilize a support vector machine to construct a feature vector for recognition. Security analysis and experiments show the effectiveness of this algorithm during the pre-processing stage, providing favorable conditions for subsequent recognition tasks and enhancing the accuracy of recognition for hollow CAPTCHA.


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Cite this article
[APA Style]
Shao, H., Xia, Y., Meng, K., & Piao, a. (2023). Study of Hollow Letter CAPTCHAs Recognition Technology Based on Color Filling Algorithm. Journal of Information Processing Systems, 19(4), 540-553. DOI: 10.3745/JIPS.02.0202.

[IEEE Style]
H. Shao, Y. Xia, K. Meng, a. C. Piao, "Study of Hollow Letter CAPTCHAs Recognition Technology Based on Color Filling Algorithm," Journal of Information Processing Systems, vol. 19, no. 4, pp. 540-553, 2023. DOI: 10.3745/JIPS.02.0202.

[ACM Style]
Huishuang Shao, Yurong Xia, Kai Meng, and and Changhao Piao. 2023. Study of Hollow Letter CAPTCHAs Recognition Technology Based on Color Filling Algorithm. Journal of Information Processing Systems, 19, 4, (2023), 540-553. DOI: 10.3745/JIPS.02.0202.