Evaluating the usability and security of the text-based CAPTCHA that asks to recognize hidden text with the help of human visual completion function 論文 Shotaro Usuzaki・Nobuya Takahashi・Taiki Kamada・Kentaro Aburada・Hisaaki Yamaba・Mirang Park・Naonobu Okazaki ·2025 ·『IEICE Communications Express』 14(12) pp. 441-444 doi:10.23919/comex.2025COL0018