Skip to main content

Research Repository

Advanced Search

Further lower bounds for structure-preserving signatures in asymmetric bilinear groups (2019)
Conference Proceeding
Ghadafi, E. (2019). Further lower bounds for structure-preserving signatures in asymmetric bilinear groups. In R. Tajjeeddine, N. Abderrahmane, & J. Buchmann (Eds.), 11th International Conference on Cryptology, AFRICACRYPT 2019https://doi.org/10.1007/978-3-030-23696-0

Structure-Preserving Signatures (SPSs) are a useful tool for the design of modular cryptographic protocols. Recent series of works have shown that by limiting the message space of those schemes to the set of Diffie-Hellman (DH) pairs, it is possible... Read More about Further lower bounds for structure-preserving signatures in asymmetric bilinear groups.

Towards a classification of non-interactive computational assumptions in cyclic groups (2017)
Conference Proceeding
Ghadafi, E., & Groth, J. (2017). Towards a classification of non-interactive computational assumptions in cyclic groups. In Advances in Cryptology – ASIACRYPT 2017, (66-96). https://doi.org/10.1007/978-3-319-70697-9_3

We study non-interactive computational intractability assumptions in prime-order cyclic groups. We focus on the broad class of computational assumptions, which we call target assumptions, where the adversary's goal is to compute a concrete group elem... Read More about Towards a classification of non-interactive computational assumptions in cyclic groups.

Linear-time zero-knowledge proofs for arithmetic circuit satisfiability (2017)
Conference Proceeding
Bootle, J., Cerulli, A., Ghadafi, E., Groth, J., Hajiabadi, M., & Jakobsen, S. K. (2017). Linear-time zero-knowledge proofs for arithmetic circuit satisfiability. In Lecture Notes in Computer Science. , (336-365). https://doi.org/10.1007/978-3-319-70700-6_12

We give computationally efficient zero-knowledge proofs of knowledge for arithmetic circuit satisfiability over a large field. For a circuit with N addition and multiplication gates, the prover only uses O(N) multiplications and the verifier only use... Read More about Linear-time zero-knowledge proofs for arithmetic circuit satisfiability.

More efficient structure-preserving signatures - or: Bypassing the type-III lower bounds (2017)
Conference Proceeding
Ghadafi, E. (2017). More efficient structure-preserving signatures - or: Bypassing the type-III lower bounds. In E. Snekkenes, D. Gollmann, & S. Foley (Eds.), https://doi.org/10.1007/978-3-319-66399-9_3

© 2017, Springer International Publishing AG. Structure-Preserving Signatures (SPSs) are an important cryptographic primitive that is useful for the design of modular cryptographic protocols. It has be shown that in the most efficient Type-III biline... Read More about More efficient structure-preserving signatures - or: Bypassing the type-III lower bounds.

Efficient round-optimal blind signatures in the standard model (2017)
Book Chapter
Ghadafi, E. (2017). Efficient round-optimal blind signatures in the standard model. In A. Kiayias (Ed.), Financial Cryptography and Data Security, (455-473). Malta: Springer Verlag

Blind signatures are at the core of e-cash systems and has numerous other applications. In this work we construct efficient blind and partially blind signature schemes over bilinear groups in the standard model. Our schemes yield short signatures co... Read More about Efficient round-optimal blind signatures in the standard model.

Foundations of fully dynamic group signatures (2016)
Conference Proceeding
Bootle, J., Cerulli, A., Chaidos, P., Ghadafi, E., & Groth, J. (2016). Foundations of fully dynamic group signatures. In Applied Cryptography and Network Security. , (117-136). https://doi.org/10.1007/978-3-319-39555-5_7

Group signatures are a central cryptographic primitive that has received a considerable amount of attention from the cryptographic community. They allow members of a group to anonymously sign on behalf of the group. Membership is overseen by a design... Read More about Foundations of fully dynamic group signatures.

Short accountable ring signatures based on DDH (2016)
Conference Proceeding
Bootle, J., Cerulli, A., Chaidos, P., Ghadafi, E., Groth, J., & Petit, C. (2016). Short accountable ring signatures based on DDH. In Computer Security -- ESORICS 2015, (243-265). https://doi.org/10.1007/978-3-319-24174-6_13

Ring signatures and group signatures are prominent cryptographic primitives offering a combination of privacy and authentication. They enable individual users to anonymously sign messages on behalf of a group of users. In ring signatures, the group,... Read More about Short accountable ring signatures based on DDH.

Short structure-preserving signatures (2016)
Journal Article
Ghadafi, E. (2016). Short structure-preserving signatures. Lecture Notes in Artificial Intelligence, 9610, 305-321. https://doi.org/10.1007/978-3-319-29485-8_18

© Springer International Publishing Switzerland 2016. We construct a new structure-preserving signature scheme in the efficient Type-III asymmetric bilinear group setting with signatures shorter than all existing schemes. Our signatures consist of 3... Read More about Short structure-preserving signatures.

Efficient distributed tag-based encryption and its application to group signatures with efficient distributed traceability (2015)
Journal Article
Ghadafi, E. (2015). Efficient distributed tag-based encryption and its application to group signatures with efficient distributed traceability. Lecture Notes in Artificial Intelligence, 8895, 327-347. https://doi.org/10.1007/978-3-319-16295-9_18

In this work, we first formalize the notion of dynamic group signatures with distributed traceability, where the capability to trace signatures is distributed among n managers without requiring any interaction. This ensures that only the participatio... Read More about Efficient distributed tag-based encryption and its application to group signatures with efficient distributed traceability.

Stronger security notions for decentralized traceable attribute-based signatures and more efficient constructions (2015)
Journal Article
Ghadafi, E. (2015). Stronger security notions for decentralized traceable attribute-based signatures and more efficient constructions. Lecture Notes in Artificial Intelligence, 9048, 391-409. https://doi.org/10.1007/978-3-319-16715-2_21

We revisit the notion of Decentralized Traceable Attribute-Based Signatures (DTABS) introduced by El Kaafarani et al. (CT-RSA 2014) and improve the state-of-the-art in three dimensions: Firstly, we provide a new stronger security model which circumve... Read More about Stronger security notions for decentralized traceable attribute-based signatures and more efficient constructions.

Attribute-based signatures with user-controlled linkability (2014)
Journal Article
El Kaafarani, A., Chen, L., Ghadafi, E., & Davenport, J. (2014). Attribute-based signatures with user-controlled linkability. Lecture Notes in Artificial Intelligence, LNCS, volume 8813, 256-269. https://doi.org/10.1007/978-3-319-12280-9_17

In this paper, we introduce Attribute-Based Signatures with User-Controlled Linkability (ABS-UCL). Attribute-based signatures allow a signer who has enough credentials/attributes to anonymously sign a message w.r.t. some public policy revealing neith... Read More about Attribute-based signatures with user-controlled linkability.

Decentralized traceable attribute-based signatures (2014)
Journal Article
El Kaafarani, A., Ghadafi, E., & Khader, D. (2014). Decentralized traceable attribute-based signatures. Lecture Notes in Artificial Intelligence, 8366 LNCS, 327-348. https://doi.org/10.1007/978-3-319-04852-9_17

We provide a formal security model for traceable attribute-based signatures. Our focus is on the more practical case where attribute management is distributed among different authorities rather than relying on a single central authority. By specializ... Read More about Decentralized traceable attribute-based signatures.

Formalizing group blind signatures and practical constructions without random oracles (2013)
Journal Article
Ghadafi, E. (2013). Formalizing group blind signatures and practical constructions without random oracles. Lecture Notes in Artificial Intelligence, 7959 LNCS, 330-346. https://doi.org/10.1007/978-3-642-39059-3_23

Group blind signatures combine anonymity properties of both group signatures and blind signatures and offer privacy for both the message to be signed and the signer. The primitive has been introduced with only informal definitions for its required se... Read More about Formalizing group blind signatures and practical constructions without random oracles.

Efficient signatures of knowledge and DAA in the standard model (2013)
Journal Article
Bernhard, D., Fuchsbauer, G., & Ghadafi, E. (2013). Efficient signatures of knowledge and DAA in the standard model. Lecture Notes in Artificial Intelligence, 7954 LNCS, 518-533. https://doi.org/10.1007/978-3-642-38980-1_33

Direct Anonymous Attestation (DAA) is one of the most complex cryptographic protocols deployed in practice. It allows an embedded secure processor known as a Trusted Platform Module (TPM) to attest to the configuration of its host computer without vi... Read More about Efficient signatures of knowledge and DAA in the standard model.

Anonymous attestation with user-controlled linkability (2013)
Journal Article
Bernhard, D., Fuchsbauer, G., Ghadafi, E., Smart, N. P., & Warinschi, B. (2013). Anonymous attestation with user-controlled linkability. International Journal of Information Security, 12(3), 219-249. https://doi.org/10.1007/s10207-013-0191-z

This paper is motivated by the observation that existing security models for direct anonymous attestation (DAA) have problems to the extent that insecure protocols may be deemed secure when analysed under these models. This is particularly disturbing... Read More about Anonymous attestation with user-controlled linkability.

Sub-linear blind ring signatures without random oracles (2013)
Book Chapter
Ghadafi, E. (2013). Sub-linear blind ring signatures without random oracles. In M. Stam (Ed.), Cryptography and Coding, 304-323. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-45239-0_18

In this paper we provide the first provably secure blind ring signature construction that does not rely on random oracles, which solves an open problem raised by Herranz and Laguillaumie at ISC 2006. We present different instantiations all of which a... Read More about Sub-linear blind ring signatures without random oracles.

Efficient two-move blind signatures in the common reference string model (2012)
Journal Article
Ghadafi, E., & Smart, N. P. (2012). Efficient two-move blind signatures in the common reference string model. Lecture Notes in Artificial Intelligence, 7483 LNCS, 274-289. https://doi.org/10.1007/978-3-642-33383-5_17

Blind signatures provide a mechanism for achieving privacy and anonymity whereby a user gets the signer to sign a message of his choice without the signer learning the message, or being able to link a signature to the protocol run via which it was ob... Read More about Efficient two-move blind signatures in the common reference string model.

Groth-Sahai proofs revisited (2010)
Journal Article
Smart, N. P., Ghadafi, E., Smart, N. P., & Warinschi, B. (2010). Groth-Sahai proofs revisited. Lecture Notes in Artificial Intelligence, 6056 LNCS, 177-192. https://doi.org/10.1007/978-3-642-13013-7_11

Since their introduction in 2008, the non-interactive zero-knowledge (NIZK) and non-interactive witness indistinguishable (NIWI) proofs designed by Groth and Sahai have been used in numerous applications. In this paper, we offer two contributions to... Read More about Groth-Sahai proofs revisited.

Practical zero-knowledge proofs for circuit evaluation (2009)
Journal Article
Ghadafi, E., Smart, N. P., & Warinschi, B. (2009). Practical zero-knowledge proofs for circuit evaluation. Lecture Notes in Artificial Intelligence, 5921 LNCS, 469-494. https://doi.org/10.1007/978-3-642-10868-6_28

Showing that a circuit is satisfiable without revealing information is a key problem in modern cryptography. The related (and more general) problem of showing that a circuit evaluates to a particular value if executed on the input contained in a publ... Read More about Practical zero-knowledge proofs for circuit evaluation.


;