Server-aided anonymous attribute-based authentication in cloud computing

• A new attribute-based signature with outsourcing compuation was proposed.
• The security model was formalized.
• The security and efficiency analysis has been given.

The notion of attribute-based signature is one of the important security primitives to realize anonymous authentication. In an attribute based signature (ABS), users can generate a signature on a message with their attributes. With this signature, any verifier will be convinced that such a signature is generated from a signer with these attributes. However, the identity of the signers will be hidden from the verifier. ABS are useful to design anonymous authentication and attribute-based messaging system. However, existing work of attribute-based authentication usually requires huge computation during signing, which grows linearly with the size of the attributes. Thus, these methods result in heavy computation overhead on the users and are not suitable for devices with only small computation ability.Cloud computing is an emerging computing paradigm in which resources of the computing infrastructure are provided as outsourcing services over the Internet. In this paper, we first address the challenging issue of securely outsourcing ABS, which enables users to largely eliminate the computational costs of ABS generation. The security model is formally defined to protect the privacy of users’ signing key while outsourcing the computation of signing. An efficient and secure outsourcing algorithm of ABS is also proposed. Extensive analysis shows that our scheme is secure in the proposed model and saves more than 90% computation overhead on the user side.