摘要：CAPTCHA is a completely automated program designed to distinguish whether
the user is a computer or human. As the problems of Internet security are
worsening, it is of great significance to do research on CAPTCHA. This article
starts from the recognition of CAPTCHAs, then analyses the weaknesses in its
design and gives corresponding recognition proposals according to various
weaknesses, finally offers suggestions related to the improvement of CAPTCHAs.
Firstly, this article briefly introduces the basic steps during the decoding
process and their principles. And during each step we choose methods which are
better adapted to the features of different CAPTCHA images. Methods chosen are
as followings: bimodal method in binarization, improved corrosion algorithm in
denoising, projection segmentation method in denoised image processing and SVM
in recognition. Then, we
demonstrate detailed process through the samples taken from the online
registration system of ICBC, show the recognition effect and correct the
results according to the statistical data in the process. This article decodes
CAPTCHAS from three other large banks in the same way but just provides the
recognition results. Finally, this article offers targeted suggestions to the
four banks based on the recognition effect and analysis process stated above.
关键词：Recognition of CAPTCHAS; Bimodal Method; Corrosion Algorithm; Projection Segmentation Method; SVM; Recommendations for Improvement
