Analysis of text-based CAPTCHA images using Template Matching Correlation technique

Author

Sakkatos, Promprawatt ; Theerayut, Weeratham ; Nuttapol, Vijitketteepragorn ; Surapong, Pongyupinpanich

Author_Institution

Comput. Eng. Dept. (RIEES Lab.), Ramkhamhaeng Univ., Bangkok, Thailand

fYear

2014

fDate

5-8 March 2014

Firstpage

1

Lastpage

5

Abstract

Text-based CAPTCHA images have been widely utilized in on-line applications to anti malicious programs which attempt to make failure in execution or computation. Although installing CAPTCHA enhances system´s security, it has to be continuously analysed, improved and developed for hard decoding or extracting from intrusion of automatic programs. This paper is mainly focused on examination of text-based CAPTCHA images with several degrees of noise, skew, font type and size. The Template Matching Correlation (TMC) technique consisting of image conversion, threshold, noise rejection, segmentation and recognition methods, is introduced for analysis. From simulation results, the robustness is increased after the image is distorted by noise background and font skew in the range of 0.3 to 0.4 and 10° to 15°; however fluently recognized by human.

Keywords

character sets; image denoising; image matching; image segmentation; Completely Automated Public Turing test to tell Computers and Humans Apart; TMC; font skew; image conversion; image recognition; image segmentation; noise background; noise rejection; template matching correlation technique; text-based CAPTCHA image analysis; threshold; CAPTCHAs; Character recognition; Image recognition; Image segmentation; Noise; Robustness; Security;

fLanguage

English

Publisher

ieee

Conference_Titel

Information and Communication Technology, Electronic and Electrical Engineering (JICTEE), 2014 4th Joint International Conference on

Conference_Location

Chiang Rai

Print_ISBN

978-1-4799-3854-4

Type

conf

DOI

10.1109/JICTEE.2014.6804098

Filename

6804098