Slight Homomorphic Signature for Access Controlling in Cloud Computing

With the popularity of cloud computing, how to securely authenticate a user while not releasing user's sensitive information becomes a challenge. In this paper, we introduce a slight homomorphic signature, which is suitable to implement an access controlling service in cloud computing. In slight homomorphic signature, each user in cloud computing who have a set of identity attributes, firstly computes a full signature on all his identity attributes, and sends it to a semi-trusted access controlling server. The access controlling server verifies the full signature for all identity attributes. After then, if the user wants to require a cloud service, which may have a special requirement on one of the identity attributes, the user only needs to securely send the cloud service's name to the access controlling server. The access controlling server which does not know the secret key can compute a partial signature on this special identity attribute, and then sends it to the cloud server for authentication. In the paper, we give a formal secure definition of this slight homomorphic signature, and construct a scheme from Boneh-Boyen signature. We prove that our scheme is secure under q-SDH problem with a weak adversary.