Research On Non - Repudiation Signature Protocol Based On Attributes

In an Attribute-Based Signature scheme, every user has his own set of at-tributes, and the user’s ability to sign only depends on his attributes. Given a message, only valid users whose attributes satisfy the signing predicate can create valid signatures, this is called unforgeability, one of the properties Attribute-Based Signature schemes should have. Another property is Privacy, which means that a valid Attribute-Based Signature only attests to the fact that a single user, whose attributes satisfy the predicate, endorsed the signature, and it is computationally infeasible to find out which attributes the signer used to create the signature, not to mention the identity of the signer. These two properties make Attribute-Based Signature schemes somewhat practical in large systems like distributed system-s and cloud environment. But most of the existing Attribute-Based Signature schemes overemphasize the privacy property and ignore the undeniability, thus malicious signers in these schemes could repudiate the signatures they signed but no one can prove it. This will strongly restrict the use of Attribute-Based Signa-ture schemes in practical applications.To introduce undeniability into Attribute-Based Signatures, we propose the concept of Undeniable Attribute-Based Signature and formally define its syntax and security properties. Undeniable Attribute-Based Signature has a good bal-ance between the privacy of signers and the undeniability of signatures:given a valid signature, any single user or trusted third party can not compute the i-dentity of the signer:while there is a Trace algorithm which can be run by the trusted third parties together to find out the identity of the signer. Besides, we give a construction of a Undeniable Attribute-Based Signature scheme and prove its existential unforgeability in the selective predicate security model under the q-Augmented Diffe-Hellman Exponent assumption in the random oracle model, we also prove its undeniability and privacy. And compared to other Attribute-Based Signature schemes, our scheme is much more efficient. Finally, we also introduce multiple authorities into this scheme and construct a Multi-Authority Undeniable Attribute-Based Signature protocol.