@article{oai:miyazaki-u.repo.nii.ac.jp:00005900,
 author = {藤, 竜成 and Fuji, Ryusei and 星野, 理彦 and Yamaba, Hisaaki and 山場, 久昭 and Aburada, Kentaro and 油田, 健太郎 and Okazaki, Naonobu and 岡崎, 直宣 and 藤, 竜成 and Fuji, Ryusei and Hoshino, Masahiko},
 journal = {宮崎大学工学部紀要, Memoirs of Faculty of Engineering, University of Miyazaki},
 month = {Jul},
 note = {Recently, a program called CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) has been introduced in many web sites because it prevents misconduct by automatic programs called bots. CAPTCHA distinguishes bots from legitimate human users by requiring some questions that are easy for human users to solve but difficult for bots. However, with the development of various technologies such as OCR, object recognition, machine learning, bots come to be able to solve CAPTCHAs. In order to outcome such troublesome bots, more sophisticated CAPTCHA is desired. In this paper, we propose a new CAPTCHA scheme that uses amodal completion. Amodal completion is a visual supplement function that complements the missing part in the brain and recognizes the whole image when a part of the object is hidden or can not be seen. In the proposed method, characters are stereoscopically rendered. We set the color of the front part and the back part of the three-dimensional characters to the same color (black) as the color used in the background of CAPTCHA. By Amodal completion, we can correctly recognize characters from only the shape of the side part of the three-dimensional characters. But it is hard for bots to recognize the characters. We carried out several experiments to confirm that the proposed CAPTCHA scheme has enough resistance against bots attacks using OCR and object recognition. Other experiments were also carried out to evaluate the usability of the proposed CAPTCHA scheme. To evaluate the usability, we used system usability scheme (SUS). The results of the experiments showed that the proposed CAPTCHA scheme is usable and has enough resistance against bots attacks.},
 pages = {251--255},
 title = {人間の視覚補完能力を用いた文字列CAPTCHAの提案 -側面形状からの立体文字の推定-},
 volume = {48},
 year = {2019},
 yomi = {フジ, リュウセイ and ホシノ, マサヒコ and ヤマバ, ヒサアキ and アブラダ, ケンタロウ and オカザキ, ナオノブ and フジ, リュウセイ}
}