Group signature with restrictive linkability: minimizing privacy exposure in ubiquitous environment

As IoT technology evolves, developments of ubiquitous computing accelerates. At the same time, threats of privacy exposure also increase since the IoT systems expose the information such as user’s location or medical status collected from all sorts of things. To handle the data elaborately, the ubiquitous systems need to employ a technology that provides anonymity to prevent exposure of personal information. The group signature scheme is widely used for a cryptographic base for privacy protection which do not reveal user’s identity but prove that he/she is a legitimate user. Recently, a number of researches concerning the basic group signature schemes with a differentiated linkability have been conducted to provide a more flexible service. However, existing researches focused on providing flexible services from the service provider’s position. The systems are exposed to high possibilities of unnecessary breach of privacy. In this paper, we define a restrictive linkability for the anonymous services that require an adequate linkability with a minimum user-designated privacy exposure in anonymous services and propose an efficient group signature scheme providing restrictive linkability.