A set of attributes instead of a single string to represent the signer’s identity is a challenging problem under standard cryptographic assumption in the standard model. Therefore, designing a fully secure (adaptive-predicate unforgeable and perfectly private) Attribute-Based Signature (ABS) that allows a signer to choose a set of attributes is vital. Existing schemes are either too complicated or have only been proved in the generic group model. In this chapter, the authors present an efficient fully secure ABS scheme in the standard model based on q-parallel BDHE assumption, which is more practical than the generic group model used in the previous schemes. The proposed scheme is highly expressive since it allows any signer to specify claim-predicates in terms of any predicate consisting of AND, OR, and Threshold gates over the attributes in the system. ABS has found many important applications in secure communications, such as anonymous authentication systems and attribute-based messaging systems.
A Practical Leakage-Resilient Signature Scheme in the Generic Group Model