Attribute-Based Signatures (ABS) is a versatile primitive which allows an entity to sign a message with fine-grained control over identifying information. A valid ABS only attests to the fact that "A single user, whose attributes satisfy the predicate, has endorsed the message". While ABS has been well investigated since its introduction, it is unfortunate that key exposure–an inherent weakness of digital signatures–has never been formally studied in the scenario of ABS. We fill this gap by proposing a new notion called forward secure ABS, its formal security models and a generic (also the first) design based on well established crypto primitives.
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