LAUSR

Attribute based signature (ABS) is a novel cryptographic primitive, which permits users to sign a message over attributes without revealing other information. A signature only reveals that it is signed by a signer whose some attributes meet an access policy. However, some ABS schemes only support the threshold access policy, where the signing algorithms are limited by the threshold. The threshold access policy cannot express precise access control well. In addition, the computation cost of the verification algorithm is heavy since pairing operations are required. Pairing is costly operation comparing to exponentiation. Therefore, existing ABS schemes are not suitable to resource-limited devices, such as RFID tags and smart cards. In order to solve the issues above, we present a novel ABS scheme by using the attribute tree as access policy that expresses flexible access control. We utilize server-aid technique to help the verifier to verify signatures and reduce the computation burden. Our scheme is proved secure against unforgeable and anonymous under chosen-policy selective-message attack in the standard model. Compared with existing schemes, our scheme is more efficient in terms of private key generation and verification. The proposed scheme reduces users calculation burden and expresses more flexible access policy.