Non-interactive zero-knowledge and its applications
STOC '88 Proceedings of the twentieth annual ACM symposium on Theory of computing
Witness indistinguishable and witness hiding protocols
STOC '90 Proceedings of the twenty-second annual ACM symposium on Theory of computing
Efficient Group Signature Schemes for Large Groups (Extended Abstract)
CRYPTO '97 Proceedings of the 17th Annual International Cryptology Conference on Advances in Cryptology
ASIACRYPT '01 Proceedings of the 7th International Conference on the Theory and Application of Cryptology and Information Security: Advances in Cryptology
Efficient Revocation in Group Signatures
PKC '01 Proceedings of the 4th International Workshop on Practice and Theory in Public Key Cryptography: Public Key Cryptography
PKC '03 Proceedings of the 6th International Workshop on Theory and Practice in Public Key Cryptography: Public Key Cryptography
On Defining Proofs of Knowledge
CRYPTO '92 Proceedings of the 12th Annual International Cryptology Conference on Advances in Cryptology
Universally Composable Security: A New Paradigm for Cryptographic Protocols
FOCS '01 Proceedings of the 42nd IEEE symposium on Foundations of Computer Science
Analysis of Anonymity on the Signatures of Knowledge
IIH-MSP '06 Proceedings of the 2006 International Conference on Intelligent Information Hiding and Multimedia
SIAM Journal on Computing
The Power of Proofs-of-Possession: Securing Multiparty Signatures against Rogue-Key Attacks
EUROCRYPT '07 Proceedings of the 26th annual international conference on Advances in Cryptology
Efficient and generalized group signatures
EUROCRYPT'97 Proceedings of the 16th annual international conference on Theory and application of cryptographic techniques
PKC'08 Proceedings of the Practice and theory in public key cryptography, 11th international conference on Public key cryptography
Efficient identity-based encryption without random oracles
EUROCRYPT'05 Proceedings of the 24th annual international conference on Theory and Applications of Cryptographic Techniques
CRYPTO'06 Proceedings of the 26th annual international conference on Advances in Cryptology
Sequential aggregate signatures and multisignatures without random oracles
EUROCRYPT'06 Proceedings of the 24th annual international conference on The Theory and Applications of Cryptographic Techniques
Ring signatures: stronger definitions, and constructions without random oracles
TCC'06 Proceedings of the Third conference on Theory of Cryptography
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We revisit the definition of signatures of knowledge by Chase and Lysanskaya (Crypto 2006) which correspond to regular signatures but where the signer also proves knowledge of the secret key to the public key through any signature. From a more abstract point of view, the signer holds a secret witness w to a public NP statement x and any signature to a message allows to extract w given some auxiliary trapdoor information. Besides extractability, Chase and Lysanskaya also demand a strong witness-hiding property, called simulatability, akin to the zero-knowledge property of non-interactive proofs. They also show that this property ensures anonymity for delegatable credentials or for ring signatures, for example. In this work here we discuss relaxed notions for simulatability and when they are sufficient for applications. Namely, in one notion we forgo any explicit witness-hiding notion, beyond some weak requirement that signatures should not help to produce further signatures, analogously to unforgeability of regular signature schemes. This notion suffices for example for devising regular signature schemes with some additional proof-of-possession (POP) or knowledge-of-secret-key (KOSK) property. Our stronger notion resembles the witness-indistinguishability notion of proofs of knowledge and can be used to build anonymous ring signatures. Besides formal definitions we relate all notions and discuss constructions and the aforementioned applications.