Expressive key-policy attribute-based constant-size signature

An attribute-based signature (ABS) scheme is a signature scheme where each signer gets the set of attributes from an attribute issuing authority and signs a message with some signing predicate which is satisfied by his/her attributes. A receiver of the signature verifies that the signature is in fact sent by someone whose attributes satisfy the signing predicate, without getting any knowledge about those attributes. In this paper, we present an ABS scheme that uses the key policy design framework. We use the bottom up approach for constructing the access structure, proposed by Emura et al. This approach is more efficient than that of top down approach, in the case when the access tree changes frequently. Our scheme supports the monotone predicates that consist of AND, OR and Threshold gates. Also, the signature generated by this scheme is of constant size that can save the bandwidth.