Author name cluster

Dawu Gu

Possible papers associated with this exact author name in Arrow. This page groups case-insensitive exact name matches and is not a full identity disambiguation profile.

7 papers

1 author row

TCS Journal 2024 Journal Article

Biometric-based two-factor authentication scheme under database leakage

Mingming Jiang
Shengli Liu
Shuai Han
Dawu Gu

A Two-Factor Authentication (2FA) scheme can authenticate a client if the client is able to provide the possession factor (like biometric feature, smart card) and the knowledge factor (like password, secret key) simultaneously. With only one factor, it is hard for an adversary to impersonate the client to pass the authentication, and thus 2FA provides better security than single-factor authentication schemes. However, as far as we know, all existing 2FA schemes do not consider the leakage of server's database, and their authenticity may fail when the database is also compromised (in addition to one factor). Considering numerous reports of database leakage in the real world, it seems imminent to study and design 2FA schemes resilient to database leakage. In this paper, we formalize security models for 2FA schemes by taking database leakage into account. Our security models consider malicious adversaries who can obtain both the client's one authentication factor and the server's database, and have two requirements, authenticity and zero-knowledge. Authenticity ensures that such malicious adversaries cannot impersonate the client to pass the authentication, while zero-knowledge guarantees that such malicious adversaries obtain no information about the client's the other factor. Zero-knowledge is especially important for biometric features (like faces, fingerprints), which are inherent to human beings and can hardly be changed. Then we propose a biometric-based 2FA scheme with biometric feature and secret key serving as the two authentication factors. Our 2FA scheme has three rounds, and we prove its authenticity and zero-knowledge under database leakage in the random oracle model. Notably, our construction makes a novel use of a recent technical advance called robust property-preserving hashing (Boyle et al. , ITCS 2019) together with fully homomorphic encryption, to recognize or discern clients by their biometric samplings in a homomorphic and secure way.

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TCS Journal 2023 Journal Article

Simulatable verifiable random function from the LWE assumption

Yiming Li
Shengli Liu
Shuai Han
Dawu Gu
Jian Weng

A verifiable random function (VRF) is a pseudorandom function F that can be publicly verified. A simulatable VRF (sVRF) is an important variant of a VRF, which additionally provides simulatability. Informally, the simulatability of a VRF depicts the ability to simulate a valid proof π that y = F ( s k, x ) for any input x and any output value y. A (simulatable) VRF can be used in the E-Cash, E-Lottery, blockchain and constructing the multi-theorem non-interactive zero-knowledge (NIZK) proof. However, up to now, the existing constructions of an sVRF either rely on non-standard assumptions (e. g. , the Q-type ones), or are built in the random oracle model, or resort to time-consuming techniques like the Cook-Levin reduction. In this paper, we design the first sVRF from the LWE assumption in the standard model (free of a random oracle) without using a Cook-Levin reduction. In our construction of an sVRF, we take as building blocks a pseudorandom function, a trapdoor fully homomorphic commitment (FHC) scheme, and a NIZK proof system for a language specified by FHC. Our trapdoor FHC is the key technical tool, which helps the simplification of the underlying NIZK language, thus making possible an instantiation of a NIZK proof from LWE without a Cook-Levin reduction. Together with an LWE-based PRF, we obtain an sVRF scheme from LWE.

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TCS Journal 2022 Journal Article

Tightly CCA-secure inner product functional encryption scheme

Xiangyu Liu
Shengli Liu
Shuai Han
Dawu Gu

Inner product functional encryption (IPFE) is a modern public key paradigm where the master key can derive a secret key s k y for a vector y, which can then be used to decrypt a ciphertext of x to get the inner product 〈 x, y 〉 as output. In ASIACRYPT 2019, Tomida proposed the first tightly secure IPFE scheme in the multi-user and multi-challenge setting based on the matrix decisional Diffie-Hellman (MDDH) assumption. However, the construction achieves CPA security only. Up to now, there is no IPFE scheme with tight CCA security available. In this paper, we construct the first tightly CCA-secure IPFE scheme in the multi-user and multi-challenge setting. The security reduction to the MDDH assumption (including SXDH, k-LIN, etc.) loses only a factor O ( log ⁡ λ ) with λ the security parameter. Moreover, our scheme enjoys full compactness. To support inner product function of dimension m, our SXDH-based IPFE has ( m 2 + 8 m + 14 ) and ( 3 m + 14 ) group elements in the master public key and ciphertext respectively. This is comparable to the tightly CPA-secure IPFE proposed by Tomida based on the DDH assumption, whose master public key and ciphertext contain ( m 2 + 2 ) and 3m group elements, respectively. Furthermore, we construct the first IPFE with both tight CCA-security and function-hiding property, based on our CCA-secure IPFE. The tight function-hiding CCA security is obtained by adapting the techniques in Lin (CRYPTO 2017) and Gay (PKC 2020) to the multi-user and multi-challenge setting.

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I&C Journal 2021 Journal Article

New cryptographic hardness for learning intersections of halfspaces over boolean cubes with membership queries

Ning Ding
Dawu Gu

We revisit the PAC learnability of the class of intersections of polynomially many halfspaces over boolean cubes in the membership query model. The previous works (Klivans-Sherstov 2009, Angluin-Kharitonov 1995) imply the unlearnability of this class based on cryptographic assumptions, which is established in the case that the learner cannot generate queries of positive labels. We investigate this issue, focusing on the case that the learner is given representations of input distributions (so it may generate queries of positive and negative labels). Our result is that assuming some new cryptographic primitives, the class is still unlearnable in the query model even if the learner has representations of the distributions. The result is established via a new argument. We show that if the class is learnable, we can come up with a differing-inputs obfuscator, which, however, does not exist given the cryptographic primitives. Thus the hardness result follows from the contradiction.

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TCS Journal 2019 Journal Article

A generic construction of tightly secure signatures in the multi-user setting

Xiao Zhang
Shengli Liu
Dawu Gu
Joseph K. Liu

In this paper, we present a generic construction of tightly secure signature schemes in the multi-user setting, which is in turn used to construct tightly secure identity-based signature schemes. Both of the securities of the constructions are based on the hardness of some subset membership problems (SMP). By instantiating SMP with the Decisional Composite Residuosity (DCR) and Matrix Decisional Diffie–Hellman (MDDH) problems, we obtain tightly secure signature schemes and tightly secure identity-based signatures based on the DCR and MDDH assumptions, respectively.

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TCS Journal 2019 Journal Article

Structure-preserving public-key encryption with leakage-resilient CCA security

Lin Lyu
Shengli Liu
Dawu Gu

Structure-preserving primitives are important building blocks in cryptographic protocols. Up to now, the only structure-preserving public-key encryption (SP-PKE) with CCA security over asymmetric pairing groups is based on the SXDH assumption, due to Libert et al. [18]. In this work, we propose a general framework of constructing SP-PKE with leakage-resilient CCA security (which implies the IND-CCA2 security). The corresponding instantiations result in the first leakage-resilient CCA secure SP-PKE from the Matrix Decision Diffie-Hellman (MDDH) assumption (including the SXDH and k-Linear assumptions) over asymmetric pairing groups. The ciphertext of our SP-PKE also enjoys the publicly verifiable property.

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TCS Journal 2019 Journal Article

Tightly secure signature schemes from the LWE and subset sum assumptions

Xiao Zhang
Shengli Liu
Jiaxin Pan
Dawu Gu

In this paper, we study how to construct tightly secure signature scheme against adaptive chosen message attacks in the multi-user setting (i. e. , tightly euf-m-cma secure signature) from the learning with errors (LWE) assumptions. More precisely, we propose a modular framework of euf-m-cma secure signature from a weak partial one-time signature (POS) scheme that is secure only against random message attacks in the multi-user setting (i. e. , euf-m-rma secure) and possesses imperfect correctness. By instantiating the weak POS with the LWE assumption, we obtain the first LWE-based tightly euf-m-cma secure signature scheme in the multi-user setting. Moreover, we also present an instantiation of the weak POS based on the Subset Sum (SS) assumption, and again we obtain the first almost tightly euf-cma secure signature scheme from the SS assumption in the single-user setting. All our security reductions are tight and without random oracles.

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