Following recent developments in digital environments, online services have become more diverse. Because of this, many users find it difficult to manage their ID and password. As such, there is a rising need for effective ID management systems. Among them, OpenID is a simple, light and usercentric ID management system. However, because of OpenID is vulnerable to phishing, so many measures being are taken to solve this problem, although no perfect anti-phishing method has so far been devised. In this paper, new anti-phishing methods using tokens and authentication e-mail are proposed. The suggested methods are based on the assumption that the number of OPs is small, and are hence safer from attack and easier to realize from the technical viewpoint than existing methods.
The traceability is one of the core requirements for group signature schemes.Recently, group signature schemes based on the bilinear mapping were proposed. The bilinearity of a bilinear mapping allows an efficient signature scheme verification for signature schemes based on the Discrete Logarithm type problem. But the bilinearity of a bilinear mapping can be an attack point with respect to the traceability for group signature schemes when it is designed in such a way that the linearity can be preserved. We show that Cheng-Zhu-Qiu-Wang's group signature schemes [8] based on bilinear mapping have no traceability property due to their improper use of a bilinear mapping in their signature generation and verification step. We also propose security enhanced group signature schemes for both of mini group signature scheme and improved group signature scheme of Cheng-Zhu-Qiu-Wang's.
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