Study On Online/Offline Attribute Based Signature

With the development of computer science and the advent of the information age, Outsourcing technology,which made people do jobs when compute resource is limited, becomes increasing popular. In outsourcing, the security and reliability concentrated people. Digital signature, as an important tool to ensure the security and reliability in outsourcing, attract more and more attention. Attribute-based signature(ABS) is one of the most important branch of digital signature.Attribute-based signature, which enables users sign messages with any predicate of their attributes issued from an attribute authority, is useful in many important applications such as anonymous authentication and attribute-based messaging systems. However, the signature computational costs scale with the complexity of the predicate has attested to the message, which makes signature a possible bottleneck for some applications. To address this problem, we propose a new on/offline scheme for ABS that splits the computation for these algorithms into two phases:a preparation phase that does the vast majority of the work to sign a message before it knows the message and the predicate has attested to the message. The second phase can then rapidly assemble an ABS signature when the specifics become known. We note that unknown message and predicate make ABS significantly more challenging. This scheme is especially suitable for resource constrained environment. When the resource is ample, we can do the offline phase. And when it is limited, online phase can be done rapidly without much resource. The main contributions of our paper are as follow:1 We have an analytic study of digital signature espically attribute-based signature and the knowledge of online/offline. By combine them, we proposed the online/offline attribute-based signature. And then we give formalized definition of attribute-based signature and security model.2 We construct a online/offline attribute-based signature scheme and then prove its correteness, privacy and unforgeability.