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Relaxed Security Notions for Signatures of Knowledge

Fischlin, Marc ; Onete, Cristina
eds.: Lopez, Javier ; Tsudik, Gene (2011)
Relaxed Security Notions for Signatures of Knowledge.
9th International Conference on Applied Cryptography and Network Security. Nerja, Spain (07.-10.06.2011)
doi: 10.1007/978-3-642-21554-4_18
Conference or Workshop Item, Bibliographie

Abstract

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.

Item Type: Conference or Workshop Item
Erschienen: 2011
Editors: Lopez, Javier ; Tsudik, Gene
Creators: Fischlin, Marc ; Onete, Cristina
Type of entry: Bibliographie
Title: Relaxed Security Notions for Signatures of Knowledge
Language: English
Date: 1 June 2011
Publisher: Springer
Book Title: Applied Cryptography and Network Security
Series: Lecture Notes in Computer Science
Series Volume: 6715
Event Title: 9th International Conference on Applied Cryptography and Network Security
Event Location: Nerja, Spain
Event Dates: 07.-10.06.2011
DOI: 10.1007/978-3-642-21554-4_18
Abstract:

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.

Divisions: 20 Department of Computer Science
20 Department of Computer Science > Cryptography and Complexity Theory
Date Deposited: 27 Jun 2011 14:44
Last Modified: 15 Aug 2023 09:56
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