| Summary: | 碩士 === 東吳大學 === 資訊管理學系 === 100 === Web CAPTCHA was first used to distinguish the user is human or robot by DEC Systems Research Center in 1997. Today's Web CAPTCHA is vulnerable to OCR, and its excessive distortions make difficult to identify; Frequent web connection of server-side Web CPATCHA generating causes congestion.
From the literature, we found that One-Time Password technique make clients create their own passwords and decrease network congestion. But, One-Time Password authentication cannot be used directly in the Web CAPTCHA structure. Thus, we change the One-Time Password scheme: S/Key for sequential passwords generating on client side (drawback: seed synchronization between client and server cannot decrease network transport times). Smart card structure can decrease network transport times, but it easily causes inconsistent and redundant password problem. By using S/Key with smart card hybrid scheme, we improve security and performance of Web CAPTCHA structure.
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