Extended attribute based encryption for private information retrieval

Private information retrieval enables the sensitive data to be obtained only if the data authorizers allow the data receivers to access to the data. Sometimes the owners are of a group and there is no need for all members to authorize the receivers. Moreover, the right to authorize could be unequal for different authorizers in the group. In this paper, we first proposed a solution providing hierarchical authorization right of different owners of the data with an extension of attribute based encryption. This scheme uses an access structure to describe the hierarchical relations of the authorizers of the data, and also provides privacy for the data and authorizer as well as the security of anti-collusion attack. In addition, we proposed an improved scheme which allows the authorizers to specify the authorization to certain data instead of providing the access right to all data they are in charge. This scheme is more secure for achieving forward security and more practical.