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Secure Attribute-based Threshold Signature without a Trusted Central Authority

Currently, in most attribute-based cryptosystem, the central authority that distributes private keys for attributes assigned to the user must be trusted unconditionally otherwise the systems will soon be collapsed. To solve the problem we propose a new attribute- based threshold signature scheme without a trusted central authority. When the number of user’s attributes reaches the threshold he can sign validly. Additionally, the central authority can be distrusted. We prove that the scheme is existentially unforgeable under selective attributes and adaptive chosen-message attack and is secure against collusion attack.