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Weakly Secure Equivalence-Class Signatures from Standard Assumptions

Georg Fuchsbauer 1 Romain Gay 2 
1 CASCADE - Construction and Analysis of Systems for Confidentiality and Authenticity of Data and Entities
DI-ENS - Département d'informatique - ENS Paris, CNRS - Centre National de la Recherche Scientifique : UMR 8548, Inria de Paris
Abstract : Structure-preserving signatures on equivalence classes, or equivalence-class signatures for short (EQS), are signature schemes defined over bilinear groups whose messages are vectors of group elements. Signatures are perfectly randomizable and given a signature on a vector, anyone can derive a signature on any multiple of the vector; EQS thus sign projective equivalence classes. Applications of EQS include the first constant-size anonymous attribute-based credentials, efficient round-optimal blind signatures without random oracles and efficient access-control encryption. To date, the only existing instantiation of EQS is proven secure in the generic-group model. In this work we show that by relaxing the definition of unforgeability, which makes it efficiently verifiable, we can construct EQS from standard assumptions, namely the Matrix-Diffie-Hellman assumptions. We then show that our unforgeability notion is sufficient for most applications.
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Submitted on : Friday, September 7, 2018 - 9:27:39 AM
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Georg Fuchsbauer, Romain Gay. Weakly Secure Equivalence-Class Signatures from Standard Assumptions. PKC 2018 - 21st IACR International Conference on Practice and Theory of Public-Key Cryptography, Mar 2018, Rio de Jaineiro, Brazil. pp.153-183, ⟨10.1007/978-3-319-76581-5_6⟩. ⟨hal-01869971⟩



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