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Huaxiong Wang

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15 papers
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15

IJCAI Conference 2025 Conference Paper

Towards Comprehensive and Prerequisite-Free Explainer for Graph Neural Networks

  • Han Zhang
  • Yan Wang
  • Guanfeng Liu
  • Pengfei Ding
  • Huaxiong Wang
  • Kwok-Yan Lam

To enhance the reliability and credibility of graph neural networks (GNNs) and improve the transparency of their decision logic, a new field of explainability of GNNs (XGNN) has emerged. However, two major limitations severely degrade the performance and hinder the generalizability of existing XGNN methods: they (a) fail to capture the complete decision logic of GNNs across diverse distributions in the entire dataset's sample space, and (b) impose strict prerequisites on edge properties and GNN internal accessibility. To address these limitations, we propose OPEN, a novel cOmprehensive and Prerequisite-free Explainer for GNNs. OPEN, as the first work in the literature, can infer and partition the entire dataset's sample space into multiple environments, each containing graphs that follow a distinct distribution. OPEN further learns the decision logic of GNNs across different distributions by sampling subgraphs from each environment and analyzing their predictions, thus eliminating the need for strict prerequisites. Experimental results demonstrate that OPEN captures nearly complete decision logic of GNNs, outperforms state-of-the-art methods in fidelity while maintaining similar efficiency, and enhances robustness in real-world scenarios.

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TCS Journal 2024 Journal Article

Group encryption: Full dynamicity, message filtering and code-based instantiation

  • Khoa Nguyen
  • Reihaneh Safavi-Naini
  • Willy Susilo
  • Huaxiong Wang
  • Yanhong Xu
  • Neng Zeng

Group encryption (GE), introduced by Kiayias, Tsiounis and Yung (Asiacrypt'07), is the encryption analogue of group signatures. It allows to send verifiably encrypted messages satisfying certain requirements to certified members of a group, while keeping the anonymity of the receivers. Similar to the tracing mechanism in group signatures, the receiver of any ciphertext can be identified by an opening authority - should the needs arise. The primitive of GE is motivated by a number of interesting privacy-preserving applications, including the filtering of encrypted emails sent to certified members of an organization. This paper aims to improve the state-of-affairs of GE systems. Our first contribution is the formalization of fully dynamic group encryption (FDGE) - a GE system simultaneously supporting dynamic user enrolments and user revocations. The latter functionality for GE has not been considered so far. As a second contribution, we realize the message filtering feature for GE based on a list of t-bit keywords and 2 commonly used policies: “permissive” - accept the message if it contains at least one of the keywords as a substring; “prohibitive” - accept the message if all of its t-bit substrings are at Hamming distance at least d from all keywords, for d ≥ 1. This feature so far has not been substantially addressed in existing instantiations of GE based on DCR, DDH, pairing-based and lattice-based assumptions. Our third contribution is the first instantiation of GE under code-based assumptions. The scheme is more efficient than the lattice-based construction of Libert et al. (Asiacrypt'16) - which, prior to our work, is the only known instantiation of GE under post-quantum assumptions. Our scheme supports the 2 suggested policies for message filtering, and in the random oracle model, it satisfies the stringent security notions for FDGE that we put forward.

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TCS Journal 2023 Journal Article

Multi-key fully homomorphic encryption from NTRU and (R)LWE with faster bootstrapping

  • Kexin Xu
  • Benjamin Hong Meng Tan
  • Li-ping Wang
  • Khin Mi Mi Aung
  • Huaxiong Wang

Multi-Key Fully Homomorphic Encryption (MKFHE) supports homomorphic evaluation on ciphertexts encrypted under different keys, guaranteeing data privacy in the case of multiple mutually untrusted parties. In ASIACRYPT 2019, Chen et al. designed an LWE-based MKFHE scheme, which evaluates a boolean gate on ciphertexts followed by a bootstrapping procedure in the dynamic multi-key setting. In this paper, we propose a new MKFHE scheme from NTRU and (R)LWE, achieving better bootstrapping performance. To that end, we adapt Chen et al. 's bootstrapping algorithm to the NTRU setting and construct an efficient conversion from multi-key NTRU to multi-key RLWE ciphertexts. With appropriate parameter choice, our scheme avoids the sublattice attacks that broke previous NTRU-based MKFHE schemes. Finally, we implement a proof-of-concept of our construction and conduct experiments to test its performance. Our experiments indicate that gate bootstrapping in our scheme for 2 parties takes 0. 18 seconds, which is faster than with Chen et al. by around 5. 3 times, but unfortunately does not scale beyond that. It is however practical for uses such as oblivious neural network inference.

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I&C Journal 2022 Journal Article

A new framework for deniable secure key exchange

  • Shaoquan Jiang
  • Yeow Meng Chee
  • San Ling
  • Huaxiong Wang
  • Chaoping Xing

A deniable secure key exchange protocol allows two parties to agree on a common secret while achieving two seemingly contradictory functionalities: authentication and deniability. The former requires each party to confirm the identity of the other while the latter requires any attacker (e. g. , participant or eavesdropper) be unable to prove to a third party an honest party's participation. Designing an efficient secure key exchange with deniability is a challenging problem. In this paper, we first formalize the deniability model by requiring information theoretic deniability with an eavesdropping attack. The information theoretic deniability has the advantage that it can hold forever without any computational assumption. An eavesdropping attack (Di Raimondo et al. , CCS'06) allows an attacker to apply eavesdropped transcripts into an active attack session. This gives an attacker more power to make the victim undeniable as he does not know the randomness of the transcript. We then propose an efficient, provably deniable secure framework of key exchange. Our deniability holds non-adaptively in the eavesdropping model. However, if we consider a model without an eavesdropping attack (which is practical in many scenarios), then our framework is proven adaptively deniable. This is important since no previous key exchange protocols can satisfy our adaptive and information theoretical deniability. We give a concrete realization for our framework that is more efficient than SKEME (Krawczyk, NDSS'96).

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TCS Journal 2021 Journal Article

Adaptive oblivious transfer with access control from lattice assumptions

  • Benoît Libert
  • San Ling
  • Fabrice Mouhartem
  • Khoa Nguyen
  • Huaxiong Wang

Adaptive oblivious transfer (OT) is a protocol where a sender initially commits to a database { M i } i = 1 N. Then, a receiver can query the sender up to k times with private indexes ρ 1, …, ρ k so as to obtain M ρ 1, …, M ρ k and nothing else. Moreover, for each i ∈ [ k ], the receiver's choice ρ i may depend on previously obtained messages { M ρ j } j < i. Oblivious transfer with access control (OT-AC) is a flavor of adaptive OT where database records are protected by distinct access control policies that specify which credentials a receiver should obtain in order to access each M i. So far, all known OT-AC protocols only support access policies made of conjunctions or rely on ad hoc assumptions in pairing-friendly groups (or both). In this paper, we provide an OT-AC protocol where access policies may consist of any branching program of polynomial length, which is sufficient to realize any access policy in NC1. The security of our protocol is proved under the Learning-with-Errors ( LWE ) and Short-Integer-Solution ( SIS ) assumptions. As a result of independent interest, we provide protocols for proving the correct evaluation of a committed branching program on a committed input.

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TCS Journal 2020 Journal Article

A code-based signature scheme from the Lyubashevsky framework

  • Yongcheng Song
  • Xinyi Huang
  • Yi Mu
  • Wei Wu
  • Huaxiong Wang

We propose a new method to construct code-based signature scheme following the Lyubashevsky's lattice-based framework. Our technique ensures that the Hamming weight of each row of the private key matrix is below the GV bound instead of fixed weight. Our scheme can generate signatures whose maximum Hamming weight is below the GV bound of random linear codes with the public key matrix as parity-check matrix. We argue that our scheme can resist existing attacks on code-based signatures. We provide a detailed security analysis and prove that our scheme is existentially unforgeable under adaptive chosen-message attacks (EUF-CMA) in the random oracle model through exploiting and expanding code-based complex problems. Our scheme enjoys the shorter signature size than the Durandal signature scheme (EUROCRYPT 2019) and the Wave signature scheme (ASIACRYPT 2019) for security level of 128 bits. We also show that there is a generic method to construct Weight Restricted Hash (WRH) functions which can produce hash value with a given Hamming weight.

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TCS Journal 2019 Journal Article

Efficient public key encryption with equality test in the standard model

  • Kai Zhang
  • Jie Chen
  • Hyung Tae Lee
  • Haifeng Qian
  • Huaxiong Wang

Public key encryption with equality test (PKEET) is a special kind of public encryption scheme (PKE) that allows a tester to perform equality tests on ciphertexts generated by different public keys as well as the same public key. This feature enables us to apply PKEET to various scenarios in practice, such as efficient data management on encrypted databases and spam filtering in encrypted email systems. From these reasons, since Yang et al. [1] first proposed the concept of PKEET, there have been proposed many PKEET schemes to improve efficiency or to enhance functionalities. However, to the best of our knowledge, almost all existing schemes were presented under assuming the existence of random oracles, except for generic construction proposed by Lee et al. On the other hand, their generic approach for PKEET employs a 2-level hierarchical identity-based encryption and a strongly unforgeable one-time signature, which suffers from low efficiency. In this paper, we propose an efficient PKEET scheme under a specific cryptographic assumption in the standard model. To this end, we first encrypt a message and its hash value in a parallel way by following the recently proposed strategy. Then, to prevent adaptive chosen ciphertext attacks (CCA2), we give a link between them by adapting the technique which was originally proposed for identity-based encryption and previously exploited to design efficient CCA2-secure PKE schemes. We show that our proposed construction satisfies formal security requirements for PKEET under the decisional bilinear Diffie–Hellman (DBDH) assumption in the standard model. As a result, we obtain a new PKEET scheme which has shorter ciphertext and trapdoor sizes, and improves computational costs for encryption, decryption, and test algorithms, by about 60%, 77%, and 66%, respectively, compared to a PKEET instantiation obtained by the prior generic framework.

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TCS Journal 2019 Journal Article

Fully homomorphic encryption over the integers for non-binary plaintexts without the sparse subset sum problem

  • Khin Mi Mi Aung
  • Hyung Tae Lee
  • Benjamin Hong Meng Tan
  • Huaxiong Wang

In this work, we solve the open problem of designing a fully homomorphic encryption scheme over the integers for non-binary plaintexts in Z Q for prime Q (Q-FHE-OI) without the hardness of the sparse subset sum problem (SSSP). Furthermore, we show that our Q-FHE-OI scheme is a useful optimization for evaluating arithmetic circuits on encrypted data for some primes. To that end, we provide a natural extension of the somewhat homomorphic encryption (SHE) scheme over the integers proposed by Cheon and Stehlé (Eurocrypt 2015) to support non-binary plaintexts. Then, a novel bootstrapping algorithm is proposed for this extended SHE scheme by introducing generalizations of several functions in binary arithmetic. As a result, we obtain a Q-FHE-OI scheme for any constant-sized prime Q ≥ 3 without the hardness of the SSSP, whose bootstrapping algorithm is asymptotically as efficient as previous best results. Beyond that, we compare the efficiency of our scheme against a Q-FHE-OI scheme obtained by emulating mod-Q gates with boolean circuits as proposed by Kim and Tibouchi (CANS 2016). Our analysis indicates our proposed scheme performs better for prime Q up to 11287, which improves on the result of Kim and Tibouchi, who showed there is at most one prime, Q = 3 where the Q-FHE-OI scheme by Nuida and Kurosawa (Eurocrypt 2015) is a better approach. This overturns our previous understanding that Q-FHE-OI schemes do not provide significant benefits.

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TCS Journal 2019 Journal Article

Lattice-based group signatures: Achieving full dynamicity (and deniability) with ease

  • San Ling
  • Khoa Nguyen
  • Huaxiong Wang
  • Yanhong Xu

Lattice-based group signature is an active research topic in recent years. Since the pioneering work by Gordon et al. (2010) [20], eight other schemes have been proposed, providing various improvements in terms of security, efficiency and functionality. However, most of the existing constructions work only in the static setting where the group population is fixed at the setup phase. The only two exceptions are the schemes by Langlois et al. (2014) [27] that handles user revocations (but new users cannot join), and by Libert et al. (2016) [28, 29] which addresses the orthogonal problem of dynamic user enrollments (but users cannot be revoked). In this work, we provide the first lattice-based group signature that offers full dynamicity (i. e. , users have the flexibility in joining and leaving the group), and thus, resolve a prominent open problem posed by previous works. Moreover, we achieve this non-trivial feat in a relatively simple manner. Starting with Libert et al. 's fully static construction (2016) [30] - which is arguably the most efficient lattice-based group signature to date, we introduce simple-but-insightful tweaks that allow to upgrade it directly into the fully dynamic setting. More startlingly, our scheme even produces slightly shorter signatures than the former, thanks to an adaptation of a technique proposed by Ling et al. (2013) [35], allowing to prove inequalities in zero-knowledge. The scheme satisfies the strong security requirements of Bootle et al. 's model (2016) [7], under the Short Integer Solution (SIS) and the Learning With Errors (LWE) assumptions. Furthermore, we demonstrate how to equip the obtained group signature scheme with the deniability functionality in a simple way. This attractive functionality, put forward by Ishida et al. (2016) [22], enables the tracing authority to provide an evidence that a given user is not the owner of a signature in question. In the process, we design a zero-knowledge protocol for proving that a given LWE ciphertext does not decrypt to a particular message.

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TCS Journal 2019 Journal Article

Zero-knowledge arguments for matrix–vector relations and lattice-based group encryption

  • Benoît Libert
  • San Ling
  • Fabrice Mouhartem
  • Khoa Nguyen
  • Huaxiong Wang

Group encryption ( GE ) is the natural encryption analogue of group signatures in that it allows verifiably encrypting messages for some anonymous member of a group while providing evidence that the receiver is a properly certified group member. Should the need arise, an opening authority is capable of identifying the receiver of any ciphertext. As introduced by Kiayias, Tsiounis and Yung (Asiacrypt'07), GE is motivated by applications in the context of oblivious retriever storage systems, anonymous third parties and hierarchical group signatures. This paper provides the first realization of group encryption under lattice assumptions. Our construction is proved secure in the standard model (assuming interaction in the proving phase) under the Learning-With-Errors ( LWE ) and Short-Integer-Solution ( SIS ) assumptions. As a crucial component of our system, we describe a new zero-knowledge argument system allowing to demonstrate that a given ciphertext is a valid encryption under some hidden but certified public key, which incurs to prove quadratic statements about LWE relations. Specifically, our protocol allows arguing knowledge of witnesses consisting of X ∈ Z q m × n, s ∈ Z q n and a small-norm e ∈ Z m which underlie a public vector b = X ⋅ s + e ∈ Z q m while simultaneously proving that the matrix X ∈ Z q m × n has been correctly certified. We believe our proof system to be useful in other applications involving zero-knowledge proofs in the lattice setting.

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TCS Journal 2018 Journal Article

A lattice-based group signature scheme with verifier-local revocation

  • San Ling
  • Khoa Nguyen
  • Adeline Roux-Langlois
  • Huaxiong Wang

Support of membership revocation is a desirable functionality for any group signature scheme. Among the known revocation approaches, verifier-local revocation (VLR) seems to be the most flexible one, because it only requires the verifiers to possess some up-to-date revocation information, but not the signers. All of the contemporary VLR group signatures operate in the bilinear map setting, and all of them will be insecure once quantum computers become a reality. In this work, we introduce the first lattice-based VLR group signature, and thus, the first such scheme that is believed to be quantum-resistant. In comparison with existing lattice-based group signatures, our scheme has several noticeable advantages: support of membership revocation, logarithmic-size signatures, and milder hardness assumptions. Moreover, our construction works without relying on public-key encryption schemes, which is an intriguing feature for group signatures.

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TCS Journal 2016 Journal Article

Analysis of Gong et al.'s CCA2-secure homomorphic encryption

  • Hyung Tae Lee
  • San Ling
  • Huaxiong Wang

It is a well-known result that homomorphic encryption is not secure against adaptive chosen ciphertext attacks (CCA2) because of its malleable property. Very recently, however, Gong et al. proposed a construction asserted to be a CCA2-secure additively homomorphic encryption (AHE) scheme; in their construction, the adversary is not able to obtain a correct answer when querying the decryption oracle on a ciphertext obtained by modifying the challenge ciphertext (Theoretical Computer Science, 2016). Because their construction is very similar to Paillier's AHE, it appeared to support an additively homomorphic property, though they did not specify an evaluation algorithm for the scheme in their paper. In this paper, we present a simple CCA2 attack on their construction by re-randomizing the challenge ciphertext. Furthermore, we look into an additively homomorphic property of their construction. To do this, we first consider a typical candidate for an addition algorithm on ciphertexts, as provided for previous AHE constructions, and establish that it does not function correctly. Subsequently, we provide plausible evidence for the hardness of achieving an additively homomorphic property with their construction. According to our analysis, it seems hard to preserve an additively homomorphic property of their construction without any modification. In addition, as a minor contribution, we point out a flaw in the decryption algorithm of their construction and present a rectified algorithm for correct decryption.

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TCS Journal 2012 Journal Article

Threshold changeable secret sharing schemes revisited

  • Zhifang Zhang
  • Yeow Meng Chee
  • San Ling
  • Mulan Liu
  • Huaxiong Wang

This paper studies the methods for changing thresholds in the absence of secure channels after the setup of threshold secret sharing schemes. First, we construct a perfect ( t, n ) threshold scheme that is threshold changeable to t ′ > t, which is optimal with respect to the share size. This improves the scheme of Wang and Wong by relaxing the requirement from q ≥ n + v to q > n with the secret-domain F q v. But these threshold changeable schemes along with most previously known schemes turn out to be insecure under the collusion attack of players holding initial shares. By adding a broadcast enforcement term we enhance the model with collusion security and N options of threshold change. Then we construct a computationally secure scheme under the enhanced model, which involves much shorter shares and broadcast messages than the perfect schemes. Finally, we discuss how to realize the enrollment and disenrollment of players, and particularly, how to deal with L-fold changes of access polices.

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TCS Journal 2001 Journal Article

Broadcast authentication for group communication

  • Rei Safavi-Naini
  • Huaxiong Wang

Traditional point-to-point message authentication systems have been extensively studied in the literature. In this paper, we consider authentication systems for group communication. The basic primitive is a multireceiver authentication system with dynamic senders (DMRA-code). In a DMRA-code any member of the group can broadcast an authenticated message to the rest of the group such that every other member of the group can individually verify the authenticity of the message. We give a flexible ‘synthesis’ construction for DMRA-codes by combining an A-code and a key distribution pattern. tDMRA-codes extend this model when there are up to t senders. We give two constructions, one algebraic and one by ‘synthesis’ of an A-code and a perfect hash family. We show universality of ‘synthesis’ constructions for unconditional and computational models of security which means that our results have wider range applications. Finally, to demonstrate the usefulness of DMRA model, we modify a secure dynamic conference-key distribution system to construct a secure dynamic conference system that provides secrecy and authenticity of communication among conferencees. The system is key-efficient as its key requirement remains nearly the same as the original conference key distribution system and so authentication is effectively obtained without any extra cost. We discuss possible extensions to this work.

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v2026.09.13