Paper 2017/801

Attribute-Based Signatures for Turing Machines

Pratish Datta and Ratna Dutta and Sourav Mukhopadhyay

Abstract

Attribute-based signatures (ABS) support restricted signing keys which allow signers to sign messages with respect to specific signing credentials or attributes that are accepted by the signing policies embedded within the signing keys. This paper presents the first ABS scheme supporting signing policies representable by Turing machines (TM), based on indistinguishability obfuscation (IO) for circuits. Our work places no constraint on the types of TM’s that can be associated with the signing keys in the sense that the TM’s can accept signing attribute strings of unbounded polynomial length and there is no limit on the description size or space complexity of the TM’s. Prior ABS schemes could support at most circuit-realizable signing policies, and consequently could deal with signing attribute strings whose lengths are fixed during setup.