Anonymous authentication: For privacy and security

This paper presents NEC's activities on anonymous authentication. Anonymous authentication is a means of authorizing a user without identification. The technology serves as a breakthrough to enhance the privacy of the user and yet preserve the security of the system. A well-known example of such an authentication scheme is called the 'group signature scheme,' where a user can be authorized as a group member without identifying the name of the member. We propose a new group signature schemes that solve the member revocation problem and the centralized authority problem. We further propose a new notion of k-times anonymous authentication, whereby unlike the group signature scheme; no authority can identify a user who has accessed less than k-times.