Niveau: Supérieur, Doctorat, Bac+8
Automorphic Signatures in Bilinear Groups and an Application to Round-Optimal Blind Signatures? Georg Fuchsbauer Ecole normale superieure, CNRS - INRIA, Paris, France Abstract We introduce the notion of automorphic signatures, which satisfy the following properties: the verification keys lie in the message space, messages and signatures consist of elements of a bilinear group, and verification is done by evaluating a set of pairing-product equations. These signatures make a perfect counterpart to the powerful proof system by Groth and Sahai (Eurocrypt 2008). We provide practical instantiations of automor- phic signatures under appropriate assumptions and use them to construct the first efficient round-optimal blind signatures. By combining them with Groth-Sahai proofs, we moreover give practical instantiations of various other cryptographic primitives, such as fully-secure group signatures, non-interactive anonymous credentials and anonymous proxy signatures. To do so, we show how to transform signature schemes whose message space is a group to a scheme that signs arbitrarily many messages at once. 1 Introduction One of the main goals of modern cryptography is anonymity. A classical primitive ensuring user anonymity is group signatures [Cv91]: they allow members that were enrolled by a group manager to sign on behalf of a group while not revealing their identity. To prevent misuse, anonymity can be revoked by an authority. Another example is anonymous credentials [Cha85], by which a user can prove that she holds a certain credential, and at the same time remain anonymous.
- group
- proofs yield efficient
- extraction key ek
- secret key
- signature
- suggest using
- groth-sahai proofs